Aquarium
Overview
 
An aquarium is a vivarium
Vivarium
A vivarium is a usually enclosed area for keeping and raising animals or plants for observation or research...

 consisting of at least one transparent side in which water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

-dwelling plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s or animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s are kept. Fishkeepers
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...

 use aquaria to keep fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s, marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...

s, turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

s, and aquatic plants. The term combines the Latin root aqua, meaning water, with the suffix -arium, meaning "a place for relating to".

An aquarist owns fish or maintains an aquarium, typically constructed of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 or high strength acrylic plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

.
Discussions
Encyclopedia
An aquarium is a vivarium
Vivarium
A vivarium is a usually enclosed area for keeping and raising animals or plants for observation or research...

 consisting of at least one transparent side in which water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

-dwelling plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s or animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...

s are kept. Fishkeepers
Fishkeeping
Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...

 use aquaria to keep fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, amphibian
Amphibian
Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s, marine mammal
Marine mammal
Marine mammals, which include seals, whales, dolphins, and walruses, form a diverse group of 128 species that rely on the ocean for their existence. They do not represent a distinct biological grouping, but rather are unified by their reliance on the marine environment for feeding. The level of...

s, turtle
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...

s, and aquatic plants. The term combines the Latin root aqua, meaning water, with the suffix -arium, meaning "a place for relating to".

An aquarist owns fish or maintains an aquarium, typically constructed of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 or high strength acrylic plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

. Cuboid
Cuboid
In geometry, a cuboid is a solid figure bounded by six faces, forming a convex polyhedron. There are two competing definitions of a cuboid in mathematical literature...

 aquaria are also known as fish tanks or simply tanks, while bowl
Bowl (vessel)
A bowl is a common open-top container used in many cultures to serve food, and is also used for drinking and storing other items. They are typically small and shallow, although some, such as punch bowls and salad bowls, are larger and often intended to serve many people.Bowls have existed for...

-shaped aquaria are also known as fish bowls. Size can range from a small glass bowl to immense public aquaria
Public aquarium
A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...

. Specialized equipment maintains appropriate water quality and other characteristics suitable for the aquarium's residents.

Antiquity

In the Roman Empire
Roman Empire
The Roman Empire was the post-Republican period of the ancient Roman civilization, characterised by an autocratic form of government and large territorial holdings in Europe and around the Mediterranean....

, the first fish to be brought indoors was the sea barbel, which was kept under guest beds in small tanks made of marble. Introduction of glass panes around the year 50 allowed Romans to replace one wall of marble tanks, improving their view of the fish. In 1369, the Chinese Emperor
Emperor of China
The Emperor of China refers to any sovereign of Imperial China reigning between the founding of Qin Dynasty of China, united by the King of Qin in 221 BCE, and the fall of Yuan Shikai's Empire of China in 1916. When referred to as the Son of Heaven , a title that predates the Qin unification, the...

, Hóngwǔ, established a porcelain
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...

 company that produced large porcelain tubs for maintaining goldfish
Goldfish
The goldfish is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish....

; over time, people produced tubs that approached the shape of modern fish bowls. Leonhard Baldner, who wrote Vogel-, Fisch- und Tierbuch (Bird, Fish, and Animal Book) in 1666, maintained weather loach
Weather loach
The Dojo Loach , is a freshwater fish in the loach family Cobitidae. They are native to Asia but are also popular as an aquarium fish...

es and newt
Newt
A newt is an aquatic amphibian of the family Salamandridae, although not all aquatic salamanders are considered newts. Newts are classified in the subfamily Pleurodelinae of the family Salamandridae, and are found in North America, Europe and Asia...

s.

Nineteenth century

In 1836, soon after his invention of the Wardian case
Wardian case
The Wardian case, was an early type of sealed protective container for plants, which found great use in the 19th Century in protecting foreign plants imported to Europe from overseas, the great majority of which had previously died from exposure during long sea journeys, frustrating the many...

, Ward proposed to use his tanks for tropical animals. In 1841 he did so, though only with aquatic plants and toy fish. However, he soon housed real animals. In 1838, Félix Dujardin
Félix Dujardin
-External sources:* @ Encyclopædia Britannica Online...

 noted owning a saltwater aquarium, though he did not use the term. In 1846, Anna Thynne maintained stony corals
Scleractinia
Scleractinia, also called stony corals, are exclusively marine animals; they are very similar to sea anemones but generate a hard skeleton. They first appeared in the Middle Triassic and replaced tabulate and rugose corals that went extinct at the end of the Permian...

 and seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...

 for almost three years, and was credited as the creator of the first balanced marine aquarium in London. At about the same time, Robert Warington experimented with a 13-gallon container, which contained goldfish, eelgrass
Vallisneria
Vallisneria is a genus of freshwater aquatic plant, commonly called eelgrass, tape grass or vallis. The genus has 6-10 species that are widely distributed, but do not grow in colder regions....

, and snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s, creating one of the first stable aquaria. He published his findings in 1850 in the Chemical Society's
Chemical Society
The Chemical Society was formed in 1841 as a result of increased interest in scientific matters....

 journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...

.

The keeping of fish in an aquarium became a popular hobby and spread quickly. In the United Kingdom, it became popular after ornate aquaria in cast iron frames were featured at the Great Exhibition
The Great Exhibition
The Great Exhibition of the Works of Industry of all Nations or The Great Exhibition, sometimes referred to as the Crystal Palace Exhibition in reference to the temporary structure in which it was held, was an international exhibition that took place in Hyde Park, London, from 1 May to 15 October...

 of 1851. In 1853, the first large public aquarium opened in the London Zoo
London Zoo
London Zoo is the world's oldest scientific zoo. It was opened in London on 27 April 1828, and was originally intended to be used as a collection for scientific study. It was eventually opened to the public in 1847...

 and came to be known as the Fish House. Philip Henry Gosse
Philip Henry Gosse
Philip Henry Gosse was an English naturalist and popularizer of natural science, virtually the inventor of the seawater aquarium, and a painstaking innovator in the study of marine biology...

 was the first person to actually use the word "aquarium", opting for this term (instead of "aquatic vivarium" or "aqua-vivarium") in 1854 in his book The Aquarium: An Unveiling of the Wonders of the Deep Sea. In this book, Gosse primarily discussed saltwater aquaria. In the 1850s, the aquarium became a fad in the United Kingdom.
Tank designs and techniques for maintaining water quality were developed by Warington, later cooperating with Gosse until his critical review of the tank water composition. Edward Edwards
Edward Edwards (zoologist)
Edward Edwards was a marine zoologist, born in Wales.Edwards was born on 23 November 1803, at Corwen, Merionethshire, where he received his education. He started in life as a draper at Bangor, Carnarvonshire, which business he carried on until 1839, when he retired from it...

 developed these glass-fronted aquaria in his 1858 patent for a "dark-water-chamber slope-back tank", with water slowly circulating to a reservoir beneath.
Germans soon rivaled the British in their interest. In 1854, an anonymous author had two articles published about the saltwater aquaria of the United Kingdom: Die Gartenlaube (The Garden House) entitled Der Ocean auf dem Tische (The Ocean on the Table). However, in 1856, Der See im Glase (The Lake in a Glass) was published, discussing freshwater aquaria, which were much easier to maintain in landlocked areas. During the 1870s, some of the first aquarist societies
Aquarium fish clubs
Aquarium fish clubs or aquarium societies are social rather than academic associations for fishkeepers. They are to be found around the world. Some clubs include members in all the different aspects of the hobby, while others concentrate on one particularly field, such as cichlids or marine...

 were appearing in Germany. The United States soon followed. Published in 1858, Henry D. Butler's The Family Aquarium was one of the first books written in the United States solely about the aquarium. According to the July issue of The North American Review of the same year, William Stimson may have owned some of the first functional aquaria, and had as many as seven or eight. The first aquarist society in the United States was founded in New York City
New York City
New York is the most populous city in the United States and the center of the New York Metropolitan Area, one of the most populous metropolitan areas in the world. New York exerts a significant impact upon global commerce, finance, media, art, fashion, research, technology, education, and...

 in 1893, followed by others. The New York Aquarium Journal, first published in October 1876, is considered to be the world's first aquarium magazine.

In the Victorian era
Victorian era
The Victorian era of British history was the period of Queen Victoria's reign from 20 June 1837 until her death on 22 January 1901. It was a long period of peace, prosperity, refined sensibilities and national self-confidence...

 in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, a common design for the home aquarium was a glass front with the other sides made of wood (made watertight with a pitch
Pitch (resin)
Pitch is the name for any of a number of viscoelastic, solid polymers. Pitch can be made from petroleum products or plants. Petroleum-derived pitch is also called bitumen. Pitch produced from plants is also known as resin. Products made from plant resin are also known as rosin.Pitch was...

 coating). The bottom would be made of slate
Slate
Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. The result is a foliated rock in which the foliation may not correspond to the original sedimentary layering...

 and heated from below. More advanced systems soon began to be introduced, along with tanks of glass in metal frames. During the latter half of the 19th century, a variety of aquarium designs were explored, such as hanging the aquarium on a wall, mounting it as part of a window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...

, or even combining it with a birdcage
Birdcage
A birdcage is a cage designed to house birds as pets.Antique birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, or of unsafe materials or construction...

.

Twentieth century

Circa 1908, the first mechanical aquarium air pump was invented, powered by running water, instead of electricity. The introduction of the air pump into the hobby is considered by several historians of the hobby to be a pivotal moment in its development.

Aquaria became more widely popular as houses had an electricity supply after World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

. Electricity
Electricity
Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

 allowed artificial lighting as well as aeration
Aeration
Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance.-Aeration of liquids:-Methods:Aeration of liquids is achieved by:...

, filtration
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...

, and heating of the water. Initially, amateur aquarists kept native fish (with the exception of goldfish); the availability of exotic species from overseas further increased the popularity of the aquarium. Jugs made from a variety of materials were used to import fish from overseas, with a bicycle foot pump
Bicycle pump
A bicycle pump is a type of positive-displacement pump specifically designed for inflating bicycle tires. It has a connection or adapter for use with one or both of the two most common types of valves used on bicycles, Schrader or Presta...

 for aeration. Plastic shipping bags were introduced in the 1950s, making it easier to ship fish. The eventual availability of air freight allowed fish to be successfully imported from distant regions. In the 1960s metal frames made marine aquaria
Marine aquarium
A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only , fish only with live rock , and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally...

 almost impossible due to corrosion, but the development of tar
Tar
Tar is modified pitch produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest...

 and silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....

 sealant allowed the first all-glass aquaria made by Martin Horowitz in Los Angeles, CA. The frames remained, however, though purely for aesthetic reasons.

In the United States, as of 1996, aquarium keeping is the second-most popular hobby after stamp collecting
Stamp collecting
Stamp collecting is the collecting of postage stamps and related objects. It is one of the world's most popular hobbies, with the number of collectors in the United States alone estimated to be over 20 million.- Collecting :...

. In 1999 it was estimated that over nine million U.S. households own an aquarium. Figures from the 2005/2006 APPMA National Pet Owners Survey report that Americans own approximately 139 million freshwater fish and 9.6 million saltwater fish. Estimates of the numbers of fish kept in aquaria in Germany suggest at least 36 million. The hobby has the strongest following in Europe, Asia, and North America. In the United States, 40 percent of aquarists maintain two or more tanks.

Materials

Most aquaria consist of glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...

 panes bonded together by silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....

, with plastic frames that are attached to the upper and lower edges for decoration. The glass aquarium is standard for sizes up to about 1000 litres (264.2 US gal). However, glass as a material is brittle and has very little give before fracturing, though generally the sealant fails first. Aquaria come in a variety of shapes such as cuboid
Cuboid
In geometry, a cuboid is a solid figure bounded by six faces, forming a convex polyhedron. There are two competing definitions of a cuboid in mathematical literature...

, hexagonal
Hexagonal prism
In geometry, the hexagonal prism is a prism with hexagonal base. The shape has 8 faces, 18 edges, and 12 vertices.Since it has eight faces, it is an octahedron. However, the term octahedron is primarily used to refer to the regular octahedron, which has eight triangular faces...

, angled to fit in a corner (L-shaped), and bow-front (the front side curves outwards). Fish bowls are generally either made of plastic or glass, and are either spherical or some other round configuration in shape.

The very first modern aquarium made of glass was developed in the 19th century by Robert Warrington. During the Victorian age it was common for glass aquaria to have slate or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 bottoms, which allowed the aquaria to be heated underneath with an open flame heat source. The aquaria in those days had the glass panels attached with metal frames and sealed with putty. These metal framed aquaria were still available on the market until the mid 1960s when the modern, silicone
Silicone
Silicones are inert, synthetic compounds with a variety of forms and uses. Typically heat-resistant and rubber-like, they are used in sealants, adhesives, lubricants, medical applications , cookware, and insulation....

-sealed style replaced them. Acrylic tanks were not generally available to the public until the 1970s.

Although glass aquaria are usually preferred by aquarists over the acrylic ones because of their resistance to scratching and much more accessible price, they come with several disadvantages. Not only are they not as crack resistant as acrylic tanks but they are also nearly two times heavier than the latter. They also provide less insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

 than acrylic aquaria and do not come in as many interesting shapes. Many aquarists or beginners who want to get fish as pets find it particularly onerous that many online suppliers will not ship glass aquaria because of the high potential for cracking and the high weight, which increases the cost of shipping. However, glass tanks are more convenient for other aquarists because unlike acrylic, glass does not yellow over time, and also because glass tanks do not need as much support as acrylic aquaria.

Even though the price is one of the main considerations for aquarists when deciding which of these two types of aquaria to purchase, when it comes to very large tanks the price difference tends to disappear.

Acrylic aquaria are also available and are the primary competitor with glass. Acrylic aquaria are stronger than glass, and much lighter. Acrylic-soluble cements are used to directly fuse acrylic together (as opposed to simply sealing the seam). Acrylic allows for the formation of unusual shapes, such as the hexagonal tank. Compared to glass, acrylics are easy to scratch; but unlike glass, it is possible to polish out scratches in acrylic.

Laminated glass
Laminated glass
Laminated glass is a type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral , between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high...

 is sometimes used, which combines the advantages of both glass and acrylic.

Large aquaria might instead use stronger materials such as fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...

-reinforced plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

s. However, this material is not transparent. Reinforced concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 is used for aquaria where weight and space are not factors. Concrete must be coated with a waterproof layer to prevent the water from breaking down the concrete as well as preventing contamination of the water by the concrete.

Styles

Aquariums have been fashioned into coffee tables, sinks, and even toilets. Another such example is the MacQuarium
Macquarium
A Macquarium is an aquarium made to sit within the shell of an Apple Macintosh computer. The term was coined by computer writer Andy Ihnatko as a joke but Macquariums have since been built both by Ihnatko himself and by others.Ihnatko originally designed his Macquarium around the Compact...

, an aquarium made from the shell of an Apple Macintosh computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

. In recent years, elaborate custom-designed home aquariums costing hundreds of thousands of dollars have become status symbols—according to The New York Times, "among people of means, a dazzling aquarium is one of the last surefire ways to impress their peers."

A kreisel tank is a circular
Circle
A circle is a simple shape of Euclidean geometry consisting of those points in a plane that are a given distance from a given point, the centre. The distance between any of the points and the centre is called the radius....

 aquarium designed to hold delicate animals such as jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

. These aquariums provide slow, circular water flow with a bare minimum of interior hardware, to prevent delicate animals from becoming injured by pumps or the tank itself. Originally a German design (kreisel means spinning top), the tank has no sharp corners, and keeps the housed animals away from the plumbing
Plumbing
Plumbing is the system of pipes and drains installed in a building for the distribution of potable drinking water and the removal of waterborne wastes, and the skilled trade of working with pipes, tubing and plumbing fixtures in such systems. A plumber is someone who installs or repairs piping...

. Water moving into the tank gives a gentle flow that keeps the inhabitants suspended, and water leaving the tank is covered by a delicate screen that prevents the inhabitants from getting stuck. There are several types of kreisel tanks. In a true kreisel, a circular tank has a circular, submerged lid. Pseudokreisels have a curved bottom surface and a flat top surface, similar to the shape of either a "U" or a semicircle
Semicircle
In mathematics , a semicircle is a two-dimensional geometric shape that forms half of a circle. Being half of a circle's 360°, the arc of a semicircle always measures 180° or a half turn...

. Stretch kreisels or Langmuir kreisels are a "double gyre" kreisel design, where the tank length is at least twice the height. Using two downwelling inlets on both sides of the tank lets gravity create two gyres in the tank. A single downwelling inlet may be used in the middle as well. The top of a stretch kreisel may be open or closed with a lid. There may also be screens about midway down the sides of the tank, or at the top on the sides. It is possible to combine these designs; a circular shaped tank is used without a lid or cover, and the surface of the water acts as the continuation of circular flow. It is now possible to start a jellyfish aquarium at home as easily as a regular fish tank.

Another popular setup is the biotope aquarium. A biotope aquarium is a recreation of a specific natural environment. Some of the most popular biotopes (to name only a few) are the Amazon river
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...

, Rio Negro River, Lake Malawi
Lake Malawi
Lake Malawi , is an African Great Lake and the southernmost lake in the Great Rift Valley system of East Africa. This lake, the third largest in Africa and the eighth largest lake in the world, is located between Malawi, Mozambique, and Tanzania...

, Lake Tanganyika
Lake Tanganyika
Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, after Lake Baikal in Siberia; it is also the world's longest freshwater lake...

, and Lake Victoria
Lake Victoria
Lake Victoria is one of the African Great Lakes. The lake was named for Queen Victoria of the United Kingdom, by John Hanning Speke, the first European to discover this lake....

. The fish, plants, substrate, rocks, wood, and any other component of the display should match that of the natural environment. It can be a real challenge to recreate such environments and most "true" biotopes will only have a few species of fish (if not only one) and invertebrates.

Aquarium size and volume

An aquarium can range from a small glass bowl containing less than 1 litres (2.1 US pt) of water to immense public aquaria that house entire ecosystems such as kelp forest
Kelp forest
Kelp forests are underwater areas with a high density of kelp. They are recognized as one of the most productive and dynamic ecosystems on Earth. Smaller areas of anchored kelp are called kelp beds....

s. Relatively large home aquaria resist rapid fluctuations of temperature and pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

, allowing for greater system stability.

Unfiltered bowl-shaped aquaria are now widely regarded as unsuitable for most fish. Advanced alternatives are now available. Aquariums should contain three forms of filtration: biological, mechanical and chemical to keep water conditions at suitable levels.

Reef aquaria under 100 litres (26.4 US gal) have a special place in the aquarium hobby; these aquaria, termed nano reefs (when used in reefkeeping), have a small water volume.

Practical limitations, most notably the weight
Weight
In science and engineering, the weight of an object is the force on the object due to gravity. Its magnitude , often denoted by an italic letter W, is the product of the mass m of the object and the magnitude of the local gravitational acceleration g; thus:...

 of water (1 kg/L) and internal water pressure (requiring thick glass siding) of a large aquarium, restrict most home aquaria to a maximum of around 1 cubic metre in volume (1000 L, weighing or ). Some aquarists, however, have constructed aquaria of many thousands of litres.

Public aquarium
Public aquarium
A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...

s designed for exhibition of large species or environments can be dramatically larger than any home aquarium. The Georgia Aquarium
Georgia Aquarium
The Georgia Aquarium, located in Atlanta, Georgia, United States, at Pemberton Place, is the world's largest aquarium with more than of marine and fresh water housing more than 120,000 animals of 500 different species...

, for example, features an individual aquarium of 6300000 gallons (23,848.1 m³).

Components

The typical hobbyist aquarium includes a filtration system, an artificial lighting system, and a heater or chiller depending on the aquarium's inhabitants. Many aquaria incorporate a hood, to decrease evaporation and prevent fish from leaving the aquarium (and anything else from entering the aquarium). They also often hold lights.

Combined biological and mechanical aquarium filtration systems
Filter (aquarium)
Aquarium filters are critical components of both freshwater and marine aquaria. Aquarium filters remove physical and soluble chemical waste products from aquaria, simplifying maintenance...

 are common. These either convert ammonia to nitrate (removing nitrogen at the expense of aquatic plants), or to sometimes remove phosphate
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...

. Filter media can house microbes that mediate nitrification
Nitrification
Nitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. Degradation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil...

. Filtration systems are the most complex component of home aquaria.

Aquarium heater
Heater (aquarium)
An aquarium heater is a device used in the fishkeeping hobby to warm the temperature of water in aquariums. Most tropical freshwater and marine aquariums are maintained at temperatures that range from 22-30 °C . The types include glass immersion heaters and undergravel heating...

s combine a heating element with a thermostat
Thermostat
A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...

, allowing the aquarist to regulate water temperature at a level above that of the surrounding air, whereas coolers and chillers (refrigeration devices) are for use anywhere, such as cold water aquaria, where the ambient room temperature is above the desired tank temperature. Thermometer
Thermometer
Developed during the 16th and 17th centuries, a thermometer is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor Developed during the 16th and 17th centuries, a thermometer (from the...

s used include glass alcohol thermometers, adhesive external plastic strip thermometers, and battery-powered LCD thermometers. In addition, some aquarists use air pumps attached to airstone
Airstone
An airstone, also called an aquarium bubbler, is a piece of aquarium furniture, traditionally a piece of limewood or porous stone, whose purpose is to gradually diffuse oxygen into the tank, eliminating the noise and large bubbles of conventional air filtration systems, and providing other benefits...

s or water pumps to increase water circulation and supply adequate gas exchange at the water surface. Wave-making devices have also been constructed to provide wave action.

An aquarium's physical characteristics form another aspect of aquarium design. Size, lighting conditions, density of floating and rooted plants, placement of bog-wood
Bog-wood
Bog-wood, also known as morta is wood from trees that have been buried in peat bogs and preserved from decay by the acidic and anaerobic bog conditions, sometimes for hundreds or even thousands of years. The wood is usually stained brown by tannins dissolved in the acidic water...

, creation of caves or overhangs, type of substrate
Substrate (aquarium)
The substrate of an aquarium refers to the material used on the tank bottom. It can affect water chemistry, filtration, and the well-being of the aquarium's inhabitants, and is also an important part of the aquarium's aesthetic appeal...

, and other factors (including an aquarium's positioning within a room) can all affect the behavior and survival of tank inhabitants.

An aquarium can be placed on an aquarium stand. Because of the weight of the aquarium, a stand must be strong as well as level. A tank that is not level may distort, leak, or crack. These are often built with cabinets to allow storage, available in many styles to match room decor. Simple metal tank stands are also available. Most aquaria should be placed on polystyrene
Polystyrene
Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry...

 to cushion any irregularities on the underlying surface or the bottom of the tank itself. However, some tanks have an underframe making this unnecessary.

Aquarium maintenance

Large volumes of water enable more stability in a tank by diluting effects from death or contamination events that push an aquarium away from equilibrium. The bigger the tank, the easier such a systemic shock
Systemic shock
A systemic shock is a shock to any system that perturbs a system enough to drive it out of equilibrium. Systemic shocks occur in a wide range of fields, ranging from medicine to economics to engineering...

 is to absorb, because the effects of that event are diluted. For example, the death of the only fish in a three U.S. gallon tank (11 L) causes dramatic changes in the system, while the death of that same fish in a 100 U.S. gallon (400 L) tank with many other fish in it represents only a minor change. For this reason, hobbyists often favor larger tanks, as they require less attention.

Several nutrient cycle
Nutrient cycle
A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of living matter. The process is regulated by food web pathways that decompose matter into mineral nutrients. Nutrient cycles occur within ecosystems...

s are important in the aquarium. Dissolved oxygen enters the system at the surface water-air interface. Similarly, carbon dioxide escapes the system into the air. The phosphate cycle is an important, although often overlooked, nutrient cycle. Sulfur, iron, and micronutrients also cycle through the system, entering as food and exiting as waste. Appropriate handling of the nitrogen cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...

, along with supplying an adequately balanced food supply and considered biological loading, is enough to keep these other nutrient cycles in approximate equilibrium.

An aquarium must be maintained regularly to ensure that the fish are kept healthy. Daily maintenance consists of checking the fish for signs of stress and disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

. Also, aquarists must make sure that the water has a good quality and it is not cloudy or foamy
Foamy
Foamy may refer to:* Having a foam-like texture* Foamy the squirrel, a character in the webtoon, Neurotically yours* Foamy the Freakadog, a briefly appearing sidekick to the eponymous superhero on the Freakazoid television show...

 and the temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 of the water is appropriate for the particular species of fish that live in the aquarium.

Typical weekly maintenance includes changing around 10-20% of the water while cleaning the gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...

, or other substrate if the aquarium has one. A good habit is to remove the water being replaced by "vacuuming" the gravel with suitable implements, as this will eliminate uneaten foods and other residues that settle on the substrate
Substrate (aquarium)
The substrate of an aquarium refers to the material used on the tank bottom. It can affect water chemistry, filtration, and the well-being of the aquarium's inhabitants, and is also an important part of the aquarium's aesthetic appeal...

. Tap water
Tap water
Tap water is a principal component of "indoor plumbing", which became available in urban areas of the developed world during the last quarter of the 19th century, and common during the mid-20th century...

 is not considered to be safe for fish to live in because it contains chemicals that harm the fish, so any tap water used must be treated with a suitable water conditioner, such as a product which removes chlorine and chloramine, and neutralises any heavy metals present. The water parameters must be checked both in the tank and in the replacing water, to make sure they are suitable for the species of fish kept.

Water conditions

The solute
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...

 content of water is perhaps the most important aspect of water conditions, as total dissolved solids
Total dissolved solids
Total Dissolved Solids is a measure of the combined content of all inorganic and organic substances contained in a liquid in: molecular, ionized or micro-granular suspended form. Generally the operational definition is that the solids must be small enough to survive filtration through a sieve...

 and other constituents dramatically impact basic water chemistry, and therefore how organisms interact with their environment. Salt content, or salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

, is the most basic measure of water conditions. An aquarium may have freshwater
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 (salinity below 500 parts per million), simulating a lake or river environment; brackish water
Brackish water
Brackish water is water that has more salinity than fresh water, but not as much as seawater. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur in brackish fossil aquifers. The word comes from the Middle Dutch root "brak," meaning "salty"...

 (a salt level of 500 to 30,000 PPM), simulating environments lying between fresh and salt, such as estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

; and salt water or seawater
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

 (a salt level of 30,000 to 40,000 PPM), simulating an ocean environment. Rarely, higher salt concentrations are maintained in specialized tanks for raising brine organisms.

Saltwater is typically alkaline, while the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 (alkali
Alkali
In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base,...

nity or acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

icity) of fresh water varies more. Hardness measures overall dissolved mineral content; hard or soft water
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...

 may be preferred. Hard water is usually alkaline, while soft water is usually neutral to acidic. Dissolved organic content
Chemical oxygen demand
In environmental chemistry, the chemical oxygen demand test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water or wastewater, making COD a useful measure of water quality...

 and dissolved gases content are also important factors.

Home aquarists typically use tap water supplied through their local water supply network
Water supply network
A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:# A drainage basin ;...

 to fill their tanks. Straight tap water cannot be used in localities that pipe chlorinated water. In the past, it was possible to "condition" the water by simply letting the water stand for a day or two, which allows the chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...

 time to dissipate. However, chloramine
Chloramine
Chloramines are derivatives of ammonia by substitution of one, two or three hydrogen atoms with chlorine atoms. Monochloramine is an inorganic compound with the formula NH2Cl. It is an unstable colourless liquid at its melting point of -66° temperature, but it is usually handled as a dilute...

 is now used more often and does not leave the water as readily. Additives
Dechlorinator
A dechlorinator is a chemical additive that removes chlorine or chloramine from water. Where tap water is chlorinated, it should be dechlorinated before use in an aquarium, since chlorine can harm aquatic life in the same way it kills micro-organisms...

 formulated to remove chlorine or chloramine are often all that is needed to make the water ready for aquarium use. Brackish or saltwater aquaria require the addition of a commercially available mixture of salts
Artificial seawater
Artificial seawater is a mixture of dissolved mineral salts that simulates seawater. Artificial seawater is primarily used in marine biology and marine aquaria, and allows the easy preparation of media appropriate for marine organisms...

 and other minerals.

Some aquarists modify water's alkalinity, hardness, or dissolved content of organics and gases, before adding it to their aquaria. This can be accomplished by additives, such as sodium bicarbonate, to raise pH. Some aquarists filter or purify their water through deionization
Purified water
Purified water is water from any source that is physically processed to remove impurities. Distilled water and deionized water have been the most common forms of purified water, but water can also be purified by other processes including reverse osmosis, carbon filtration, microfiltration,...

 or reverse osmosis
Reverse osmosis
Reverse osmosis is a membrane technical filtration method that removes many types of large molecules and ions from solutions by applying pressure to the solution when it is on one side of a selective membrane. The result is that the solute is retained on the pressurized side of the membrane and...

 prior to using it. In contrast, public aquaria with large water needs often locate themselves near a natural water source (such as a river, lake, or ocean) to reduce the level of treatment. Some hobbyists use an algae scrubber
Algae scrubber
An algae scrubber is a water filtering device which uses light to grow algae; in this process, undesirable chemicals are removed from the water...

 to filter the water naturally.

Water temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 determines the two most basic aquarium classifications: tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately  N and the Tropic of Capricorn in the southern hemisphere at  S; these latitudes correspond to the axial tilt of the Earth...

 versus cold water
Coldwater fish
Coldwater fish, in the context of aquariums, refers to fish species that prefer cooler water temperatures than tropical fish, typically below . Some examples are koi and goldfish...

. Most fish and plant species tolerate only a limited temperature range; tropical aquaria, with an average temperature of about 25 °C (77 °F), are much more common. Cold water aquaria are for fish that are better suited to a cooler environment. More important than the range is consistency; most organisms are not accustomed to sudden changes in temperatures, which can cause shock and lead to disease. Water temperature can be regulated with a thermostat
Thermostat
A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...

 and heater (or cooler).

Water movement can also be important in simulating a natural ecosystem. Aquarists may prefer anything from still water up to swift currents, depending on the aquarium's inhabitants. Water movement can be controlled via aeration from air pumps, powerheads, and careful design of internal water flow (such as location of filtration system points of inflow and outflow).

Nitrogen cycle

Of primary concern to the aquarist is management of the waste
Waste
Waste is unwanted or useless materials. In biology, waste is any of the many unwanted substances or toxins that are expelled from living organisms, metabolic waste; such as urea, sweat or feces. Litter is waste which has been disposed of improperly...

 produced by an aquarium's inhabitants. Fish, invertebrates, fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

, and some bacteria excrete nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 waste in the form of ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 (which converts to ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

, in acidic water) and must then pass through the nitrogen cycle
Nitrogen cycle
The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out by both biological and non-biological processes. Important processes in the nitrogen cycle include fixation, mineralization, nitrification, and denitrification...

. Ammonia is also produced through the decomposition
Decomposition
Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

 of plant and animal matter, including fecal
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...

 matter and other detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...

. Nitrogen waste products become toxic to fish and other aquarium inhabitants at high concentrations.

The process

A well-balanced tank contains organisms that are able to metabolize
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 the waste products of other aquarium residents. This process is known in the aquarium hobby as the nitrogen cycle. Bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 known as nitrifiers
Nitrification
Nitrification is the biological oxidation of ammonia with oxygen into nitrite followed by the oxidation of these nitrites into nitrates. Degradation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil...

 (genus Nitrosomonas
Nitrosomonas
Nitrosomonas is a genus comprising rod shaped chemoautotrophic bacteria.This rare bacteria oxidizes ammonia into nitrite as a metabolic process. Nitrosomonas are useful in treatment of industrial and sewage waste and in the process of bioremediation. They are important in the nitrogen cycle by...

) metabolize nitrogen waste. Nitrifying bacteria capture ammonia from the water and metabolize it to produce nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

. Nitrite is toxic to fish in high concentrations. Another type of bacteria (genus Nitrospira) converts nitrite into nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

, a less toxic substance. (Nitrobacter
Nitrobacter
Nitrobacter is genus of mostly rod-shaped, gram-negative, and chemoautotrophic bacteria.Nitrobacter plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil...

bacteria were previously believed to fill this role. While biologically they could theoretically fill the same niche as Nitrospira, it has recently been found that Nitrobacter are not present in detectable levels in established aquaria, while Nitrospira are plentiful.) However, commercial products sold as kits to "jump start" the nitrogen cycle often still contain Nitrobacter.

In addition to bacteria, aquatic plants also eliminate nitrogen waste by metabolizing ammonia and nitrate. When plants metabolize nitrogen compounds, they remove nitrogen from the water by using it to build biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 that decays more slowly than ammonia-driven plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

 already dissolved in the water.

Maintaining the nitrogen cycle

What hobbyists call the nitrogen cycle is only a portion of the complete cycle: nitrogen must be added to the system (usually through food provided to the tank inhabitants), and nitrates accumulate in the water at the end of the process, or become bound in the biomass of plants. The aquarium keeper must remove water once nitrate concentrations grow, or remove plants which have grown from the nitrates.

Hobbyist aquaria often do not have sufficient bacteria populations to adequately denitrify waste. This problem is most often addressed through two filtration
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...

 solutions: Activated carbon
Activated carbon
Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.The word activated in the name is sometimes replaced...

 filters absorb nitrogen compounds and other toxins, while biological filters provide a medium designed to enhance bacterial colonization
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in colonies...

. Activated carbon and other substances, such as ammonia absorbing resins, stop working when their pores fill, so these components have to be replaced regularly.

New aquaria often have problems associated with the nitrogen cycle due to insufficient beneficial bacteria. Therefore fresh water has to be matured before stocking them with fish. There are three basic approaches to this: the "fishless cycle", the "silent cycle" and "slow growth".

In a fishless cycle
Fishless cycling
Fishless cycling is a form of "maturing" an aquarium. In this process, ammonia is provided to allow beneficial bacteria to colonize. Fishless cycling can reduce the chance of fish loss resulting from insufficient populations of these bacteria.- Process :...

, small amounts of ammonia are added to an unpopulated tank to feed the bacteria. During this process, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, nitrite
Nitrite
The nitrite ion has the chemical formula NO2−. The anion is symmetric with equal N-O bond lengths and a O-N-O bond angle of ca. 120°. On protonation the unstable weak acid nitrous acid is produced. Nitrite can be oxidised or reduced, with product somewhat dependent on the oxidizing/reducing agent...

, and nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

 levels are tested to monitor progress. The "silent" cycle is basically nothing more than densely stocking the aquarium with fast-growing aquatic plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s and relying on them to consume the nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, allowing the necessary bacterial populations time to develop. According to anecdotal reports, the plants can consume nitrogenous waste so efficiently that ammonia and nitrite level spikes seen in more traditional cycling methods are greatly reduced or disappear. "Slow growth" entails slowly increasing the population of fish over a period of 6 to 8 weeks, giving bacteria colonies time to grow and stabilize with the increase in fish waste. This method is usually done with a small starter population of hardier fish which can survive the ammonia and nitrite spikes, whether they are intended to be permanent residents or to be traded out later for the desired occupants.

The largest bacterial populations are found in the filter, where is high water flow and plentiful surface available for their growth, so effective and efficient filtration is vital. Sometimes, a vigorous cleaning of the filter is enough to seriously disturb the biological balance of an aquarium. Therefore, it is recommended to rinse mechanical filters in an outside bucket of aquarium water to dislodge organic materials that contribute to nitrate problems, while preserving bacteria populations. Another safe practice consists of cleaning only half of the filter media during each service, or using two filters, only one of which is cleaned at a time.

Biological loading

Biological load is a measure of the burden placed on the aquarium ecosystem by its inhabitants. High biological loading presents a more complicated tank ecology, which in turn means that equilibrium is easier to upset. Several fundamental constraints on biological loading depend on aquarium size. The water's surface area
Surface area
Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...

 limits oxygen
Oxygen saturation
Oxygen saturation or dissolved oxygen is a relative measure of the amount of oxygen that is dissolved or carried in a given medium. It can be measured with a dissolved oxygen probe such as an oxygen sensor or an optode in liquid media, usually water.It has particular significance in medicine and...

 intake. The bacteria population depends on the physical space they have available to colonize. Physically, only a limited size and number of plants and animals can fit into an aquarium while still providing room for movement. Biologically, biological loading refers to the rate of biological decay in proportion to tank volume.

Calculating capacity

Limiting factor
Limiting factor
A limiting factor or limiting resource is a factor that controls a process, such as organism growth or species population, size, or distribution. The availability of food, predation pressure, or availability of shelter are examples of factors that could be limiting for an organism...

s include the oxygen availability and filtration processing. Aquarists have rules of thumb
Rule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...

 to estimate the number of fish that can be kept in an aquarium. The examples below are for small freshwater fish; larger freshwater fishes and most marine fishes need much more generous allowances.
  • 3 cm of adult fish length per 4 litres of water (i.e., a 6 cm-long fish would need about 8 litres of water).
  • 1 cm of adult fish length per 30 square centimetres of surface area.
  • 1 inch of adult fish length per US gallon of water.
  • 1 inch of adult fish length per 12 square inches of surface area.


Experienced aquarists warn against applying these rules too strictly because they do not consider other important issues such as growth rate, activity level, social behaviour, surface area of plant life, and so on. Establishing maximum capacity is often a matter of slowly adding fish and monitoring water quality over time, following a trial and error
Trial and error
Trial and error, or trial by error, is a general method of problem solving, fixing things, or for obtaining knowledge."Learning doesn't happen from failure itself but rather from analyzing the failure, making a change, and then trying again."...

 approach.

Other factors affecting capacity

One variable is differences between fish. Smaller fish consume more oxygen per gram of body weight than larger fish. Labyrinth fish can breathe atmospheric oxygen and do not need as much surface area (however, some of these fish are territorial, and do not appreciate crowding). Barbs also require more surface area than tetra
Tetra
thumb|right|250px|Pristella tetra — [[Pristella maxillaris]].thumb|right|250px|Golden Pristella tetra, a [[morph |morph]] of [[Pristella maxillaris]].thumb|right|250px|[[Silvertip tetra]] — Hasemania nana....

s of comparable size.

Oxygen exchange at the surface is an important constraint, and thus the surface area of the aquarium matters. Some aquarists claim that a deeper aquarium holds no more fish than a shallower aquarium with the same surface area. The capacity can be improved by surface movement and water circulation such as through aeration, which not only improves oxygen exchange, but also waste decomposition rates.

Waste density is another variable. Decomposition in solution consumes oxygen. Oxygen dissolves less readily in warmer water; this is a double-edged sword since warmer temperatures make fish more active, so they consume more oxygen.

In addition to bioload/chemical considerations, aquarists also consider the mutual compatibility of the fish. For instance, predatory fish are usually not kept with small, passive species, and territorial fish are often unsuitable tankmates for shoaling species. Furthermore, fish tend to fare better if given tanks conducive to their size. That is, large fish need large tanks and small fish can do well in smaller tanks. Lastly, the tank can become overcrowded without being overstocked. In other words, the aquarium can be suitable with regard to filtration capacity, oxygen load, and water, yet still be so crowded that the inhabitants are uncomfortable.

Aquarium classifications

From the outdoor ponds and glass jars of antiquity, modern aquaria have evolved into a wide range of specialized systems. Individual aquaria can vary in size from a small bowl large enough for only a single small fish, to the huge public aquaria that can simulate entire marine ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....

s.

One way to classify aquaria is by salinity. Freshwater aquaria
Freshwater aquarium
A freshwater aquarium is a receptacle that holds one or more freshwater aquatic organisms for decorative, pet-keeping, or research purposes. Modern aquariums are most often made from transparent glass or acrylic glass. Typical inhabitants include fish, plants, amphibians, and invertebrates, such as...

 are the most popular due to their lower cost.More expensive and complex equipment is required to set up and maintain a marine aquaria
Marine aquarium
A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only , fish only with live rock , and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally...

. Marine aquaria frequently feature a diverse range of invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s in addition to species of fish. Brackish water aquaria
Brackish-water aquarium
A brackish water aquarium is an aquarium where the water is brackish . The range of "saltiness" varies greatly, from near freshwater to near marine and is often referred to as specific gravity or salinity. Brackish water aquaria is a popular specialization within the fishkeeping hobby...

 combine elements of both marine and freshwater fishkeeping. Fish kept in brackish water aquaria generally come from habitats with varying salinity, such as mangrove swamp
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...

s and estuaries. Subtypes exist within these types, such as the reef aquarium
Reef aquarium
A reef aquarium or reef tank is an marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the coral reef environment...

, a typically smaller marine aquarium that houses coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

.

Another classification is by temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

 range. Many aquarists choose a tropical aquarium
Tropical fish
Tropical fish include fish found in tropical environments around the world, including both freshwater and salt water species.Tropical fish are popular as aquarium fish, due to their often bright coloration...

 because tropical fish tend to be more colorful. However, the coldwater aquarium
Coldwater fish
Coldwater fish, in the context of aquariums, refers to fish species that prefer cooler water temperatures than tropical fish, typically below . Some examples are koi and goldfish...

 is also popular, which is mainly restricted to goldfish
Goldfish
The goldfish is a freshwater fish in the family Cyprinidae of order Cypriniformes. It was one of the earliest fish to be domesticated, and is one of the most commonly kept aquarium fish....

, but can include fish from temperate areas worldwide and native fish keeping.
Aquaria may be grouped by their species selection. The community tank
Community tank
Community aquaria are tanks that are designed to contain more than one species of fish. Most commonly they include a variety of species that do not normally occur together in nature, for example angelfish from Brazil, swordtails from Mexico, and gouramis from South East Asia...

 is the most common today, where several non-aggressive species live peacefully. In these aquaria, the fish, invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

s, and plants
Aquatic plant
Aquatic plants are plants that have adapted to living in aquatic environments. They are also referred to as hydrophytes or aquatic macrophytes. These plants require special adaptations for living submerged in water, or at the water's surface. Aquatic plants can only grow in water or in soil that is...

 probably do not originate from the same geographic region, but tolerate similar water conditions. Aggressive tanks, in contrast, house a limited number of species that can be aggressive toward other fish, or are able to withstand aggression well. Most marine tanks and tanks housing cichlids have to take the aggressiveness of the desired species into account when stocking. Specimen tanks usually only house one fish species, along with plants, perhaps ones found in the fishes' natural environment and decorations simulating a natural ecosystem. This type is useful for fish that cannot coexist with other fish, such as the electric eel
Electric eel
The electric eel , is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, of up to six hundred volts, which it uses for both hunting and self-defense. It is an apex predator in its South American range...

, as an extreme example. Some tanks of this sort are used simply to house adults for breeding.

Ecotype, ecotope, or biotope
Biotope
Biotope is an area of uniform environmental conditions providing a living place for a specific assemblage of plants and animals. Biotope is almost synonymous with the term habitat, but while the subject of a habitat is a species or a population, the subject of a biotope is a biological community.It...

 aquaria is another type based on species selection. In it, an aquarist attempts to simulate a specific natural ecosystem, assembling fish, invertebrate species, plants, decorations and water conditions all found in that ecosystem. These biotope aquaria are the most sophisticated hobby aquaria; public aquaria use this approach whenever possible. This approach best simulates the experience of observing in the wild. It typically serves as the healthiest possible artificial environment for the tank's occupants.

Public aquaria

Most public aquarium facilities feature a number of smaller aquaria, as well those too large for home aquarists. The largest tanks hold millions of gallons of water and can house large species, including shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s or beluga whales. Dolphinaria
Dolphinarium
A dolphinarium is an aquarium for dolphins. The dolphins are usually kept in a large pool, though occasionally they may be kept in pens in the open sea, either for research or for public performances...

 are specifically for dolphins. Aquatic and semiaquatic animals, including otter
Otter
The Otters are twelve species of semi-aquatic mammals which feed on fish and shellfish, and also other invertebrates, amphibians, birds and small mammals....

s and penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...

s, may also be kept by public aquaria. Public aquaria may also be included in larger establishments such as a marine mammal park
Marine mammal park
A marine mammal park is a commercial theme park or aquarium where marine mammals such as dolphins, beluga whales and sea lions are kept within water tanks and displayed to the public in special shows. A marine mammal park is more elaborate than a dolphinarium, because it also features other marine...

 or a marine park
Marine park
A marine park is a park consisting of an area of sea sometimes protected for recreational use, but more often set aside to preserve a specific habitat and ensure the ecosystem is sustained for the organisms that exist there...

.

Virtual aquariums

A virtual aquarium is a computer program
Computer program
A computer program is a sequence of instructions written to perform a specified task with a computer. A computer requires programs to function, typically executing the program's instructions in a central processor. The program has an executable form that the computer can use directly to execute...

 which uses 3D graphics to reproduce an aquarium on a personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

. The swimming fish are rendered
Rendering (computer graphics)
Rendering is the process of generating an image from a model , by means of computer programs. A scene file contains objects in a strictly defined language or data structure; it would contain geometry, viewpoint, texture, lighting, and shading information as a description of the virtual scene...

 in real time
Real-time computer graphics
Real-time computer graphics is the subfield of computer graphics focused on producing and analyzing images in real time. The term is most often used in reference to interactive 3D computer graphics, typically using a GPU, with video games the most noticeable users...

, while the background of the tank is usually static. Objects on the floor of the tank may be mapped in simple planes so that the fish may appear to swim both in front and behind them, but a relatively simple 3D map of the general shape of such objects may be used to allow the light and ripples on the surface of the water to cast realistic shadow
Shadow
A shadow is an area where direct light from a light source cannot reach due to obstruction by an object. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the...

s. Bubbles and water noises are common for virtual aquariums, which are often used as screensaver
Screensaver
A screensaver is a type of computer program initially designed to prevent phosphor burn-in on CRT and plasma computer monitors by blanking the screen or filling it with moving images or patterns when the computer is not in use...

s.

The number of each type of fish can usually be selected, often including other animals like starfish, jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, seahorse
Seahorse
Seahorses compose the fish genus Hippocampus within the family Syngnathidae, in order Syngnathiformes. Syngnathidae also includes the pipefishes. "Hippocampus" comes from the Ancient Greek hippos meaning "horse" and kampos meaning “sea monster”.There are nearly 50 species of seahorse...

s, and even sea turtle
Sea turtle
Sea turtles are marine reptiles that inhabit all of the world's oceans except the Arctic.-Distribution:...

s. Most companies that produce virtual aquarium software also offer other types of fish for sale via Internet download. Other objects found in an aquarium can also be added and rearranged on some software, like treasure chest
Treasure Chest
Treasure Chest was a Catholic-oriented comic book series created by Dayton, Ohio publisher George A...

s and giant clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...

s that open and close with air bubbles, or a bobbing diver
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

. There are also usually features that allow the user to tap on the glass or put food in the top, both of which the fish will react to. Some also have the ability to allow the user to edit fish and other objects to create new varieties.

See also

  • Aquascaping
    Aquascaping
    Aquascaping is the craft of arranging aquatic plants, as well as rocks, stones, cavework, or driftwood, in an aesthetically pleasing manner within an aquarium—in effect, gardening under water. Aquascape designs include a number of distinct styles, including the garden-like Dutch style and the...

  • Association of Zoos and Aquariums
    Association of Zoos and Aquariums
    The Association of Zoos and Aquariums was founded in 1924 and is a nonprofit organization dedicated to the advancement of zoos and public aquariums in the areas of conservation, education, science, and recreation.The AZA headquarters is located in Silver...

     (AZA)
  • Filter (aquarium)
    Filter (aquarium)
    Aquarium filters are critical components of both freshwater and marine aquaria. Aquarium filters remove physical and soluble chemical waste products from aquaria, simplifying maintenance...

  • Fishkeeping
    Fishkeeping
    Fishkeeping is a popular hobby concerned with keeping fish in a home aquarium or garden pond. There is also a fishkeeping industry, as a branch of agriculture.-Types of fishkeeping systems:...

  • List of aquarium diseases
  • List of aquarium fish by scientific name
  • List of brackish aquarium fish species
  • List of brackish aquarium plant species
  • List of freshwater aquarium amphibian species
  • List of freshwater aquarium fish species
  • List of freshwater aquarium invertebrate species
  • List of freshwater aquarium plant species
  • List of marine aquarium fish species
  • List of marine aquarium invertebrate species
  • List of marine aquarium plant species
  • MacQuarium
    Macquarium
    A Macquarium is an aquarium made to sit within the shell of an Apple Macintosh computer. The term was coined by computer writer Andy Ihnatko as a joke but Macquariums have since been built both by Ihnatko himself and by others.Ihnatko originally designed his Macquarium around the Compact...

  • Oceanarium
    Oceanarium
    An oceanarium can be either a marine mammal park, such as Marineland of Florida, or a large-scale aquarium, such as the Lisbon Oceanarium, presenting an ocean habitat with marine animals, especially large ocean dwellers such as sharks.- Marine mammal parks :...

  • Public aquarium
    Public aquarium
    A public aquarium is the aquatic counterpart of a zoo, housing living aquatic species for viewing. Most public aquariums feature tanks larger than those kept by home aquarists, as well as smaller tanks. Since the first public aquariums were built in the mid-19th century, they have become popular...

  • Reef aquarium
    Reef aquarium
    A reef aquarium or reef tank is an marine aquarium that prominently displays live corals and other marine invertebrates as well as fish that play a role in maintaining the coral reef environment...

  • Vivarium
    Vivarium
    A vivarium is a usually enclosed area for keeping and raising animals or plants for observation or research...


External links

  • The Aquarium Wiki
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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