Dropsy is a common disease among fresh-water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 aquarium

Aquarium

An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

 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...

. It is characterized by a swollen or hollow abdomen. The name is from an old name for Edema

Edema

Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...

 in humans.

Symptoms

In dropsy, a concentration of fluid in the body tissues and cavities causes the fish's abdomen to become swollen and appear bloated (Ascites

Ascites

Ascites is a gastroenterological term for an accumulation of fluid in the peritoneal cavity.The medical condition is also known as peritoneal cavity fluid, peritoneal fluid excess, hydroperitoneum or more archaically as abdominal dropsy. Although most commonly due to cirrhosis and severe liver...

). Swollen areas may exhibit a 'pine-cone' appearance caused by the fish's scales sticking out. Fish may also stop feeding, appear off-color, become listless and/or lethargic, have sunken eyes, and hang at the top or stay at the bottom of the aquarium. The condition affects the fish's internal organs, ceasing proper function.

Causes

The cause of fish dropsy can be difficult to diagnose. The main cause is bacterial infection. The causative agent may be introduced through poor water quality. Kidney failure or excess fluid (ascites) due to liver

Liver failure

Acute liver failure is the appearance of severe complications rapidly after the first signs of liver disease , and indicates that the liver has sustained severe damage . The complications are hepatic encephalopathy and impaired protein synthesis...

 or heart failure are other possible causes.

Treatment

Because dropsy is a symptom of an illness, it may or may not be contagious. However, it is standard practice to quarantine

Quarantine

Quarantine is compulsory isolation, typically to contain the spread of something considered dangerous, often but not always disease. The word comes from the Italian quarantena, meaning forty-day period....

sick fish to prevent stress among the other fish in the tank community. This extra stress may make the others vulnerable to dropsy or other forms of disease.

Prognosis

Most cases of dropsy are fatal if not treated correctly. By the time the fish has swollen up enough that the scales begin to rise, the internal damage may be too extensive to repair.

Prevention

Water quality is an important factor in prevention of fish disease. Water changes will dilute existing disease agents, and reduce stress on the tank occupants.