Fish Diseases: Diagnosis

The following are a few diseases that you must be able to identify while choosing a fish, whether it be from breeders or from a pet store. One of the main keys to a tank being diseased, is the color of the water. If the water appears to be a blue or green color, that is an indication that it is being treated for sickness.


If you find several fish in the tank that are scraping or “hitting” themselves against tank fixtures, wiggling drastically back and forth in place, or have white growths like fungus or cysts, you might want to reconsider buying anything from that tank. If you decide to buy a fish from tanks that exhibit these mentioned symptoms, be sure to place the fish in a hospital tank from 7-30 days before adding to a community of fish.

Some of these diseases are very apparent, some of them are hard to see, or impossible to diagnose until the fish is dead and you have it examined under a microscope. It is very important to quarantine new fishes for 7-30 days before introducing them into your breeding community. While the learning never stops, eventually you will find yourself moving on instinct and experience!

Abnormal Growths:

A wide variety of tumors appear on guppies most often. Some are benign, some are malignant. If found in your stock or fry, it is best to destroy the fish.

Bacterial Diseases:

Air Bladder Disease: Some fish with air bladder problems lie on the bottom of the tank and make efforts to rise, only to relax to the bottom again. Others may float and be unable to swim downward. This is because of inflamed organs that reduce the size of the air bladder, or inflammation of the air bladder.

Bloat: Scales appear to stand on end, and fish looks bloated. This may be signs of an intestinal infection. Fish cannot swim below the surface without exertion, and many stay in upright position.

Gas Bubble Disease: There isn’t an exact, known cause for this disease. Bacteria invades portions of the fish’s body, and then collects in areas. EXAMPLE: Collects behind the eyes and pops them forward.

Shrinking: Fish seems to “shrink”, the abdomen becomes smaller, the fish’s bottom becomes straight; is found in many females. Fish quickly dies. Condition may be caused by Turbuculosis, or high acidity in water.

Turberculosis: This disease is very slow, and the fish does not waste away. This disease shows few symptoms, resulting in the death of numerous fish. Does not spread through the tank.