Aquatics Unlimited: Articles: Fat Fish III: Kidney Disease
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Fat Fish III: Kidney Disease

for the week of 6/17/99

In freshwater fish, the main function of the kidneys are to expel water that is constantly entering the cells by osmosis. If the kidneys fail or are weakened, the fish begins to balloon up with excess water, leading to conditions often called "dropsy" or "Malawi bloat."

What causes kidney problems? Parasitic, bacterial and viral infections can all damage kidneys, as can exposure to toxins. While not a common problem in any species, certain fish, such as dwarf gouramis and some of the "mbuna" African Cichlids, appear to be pre-disposed to these infections.

What are the symptoms? Fish with kidney problems usually swell quickly, from normal to very distorted within a few days. The skin may stretch so much that scales begin to stand on end, and the eyes may also begin to bulge. Generally, only one fish is sick at a time. Fish usually refuse food after a few days, but continue to balloon, and death follows within a few weeks.

Can it be prevented? There appears to be a link between "Malawi Bloat" and overfeeding or inadequate roughage and "Dropsy" seems more common in dirty water type conditions. Good aquarium husbandry reduces the risk of these and most other problems.

Is there treatment? Occasionally, fish recover after receiving antibiotic treatment, preferably by injection, but sometimes by high-strength, short-term baths. In general, however, fish are beyond hope of recovery before the disease is noticed. Infected fish are best removed from the community aquarium well before death to avoid the risk of disease transfer as other fish feed on the deceased.


"Tip of the week" appeared regularly in 1999 and 2000.

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