Common Fish Diseases

That Pet Place


2/26/2018 5:04 pm

Ich, Dropsy, & Swim Bladder Disease

Fish disease and illness can be broken down into 3 main groups: Bacterial, Parasites, and Fungus.


Ich, or ick, is a common problem in all aquariums. The disease is caused by a protozoan parasite, Ichthyophthirius multifiliis, and is very contagious. The parasites spend a portion of their life cycle embedded beneath the skin of the fish, where they feed from the body tissue. The white cyst in which they are enclosed gives the characteristic white spots. Adults emerge from these cysts and fall to the floor of the aquarium, where they multiply inside a protective capsule. Sometime later, the capsule bursts, releasing hundreds of free-swimming infectious parasites which attach themselves to new hosts. White spot is often introduced with new fish which have not been quarantined. Outbreaks of white spot often occur after fish have been exposed to cooler than normal temperatures. Any medication you add to your tank to get rid of ich will only kill those free swimming parasites! So be prepared to treat your tank for a long time (even a few weeks) as you wait for the white spots to become the free-swimming stage. When treating ich, it is a good idea to crank up the heater to as high as your fish can stand, probably around 82°. The higher temperature causes ich's lifecycle to speed up and they will start the free-swimming stage quicker so you can kill them sooner!


This is an internal bacterial infection that causes multi-organ failure, and is very difficult to treat. The fish often look like "pine-cones", with their scales sticking out, off of their body. They are often listless, won't eat, and sit at the bottom or in one area of the aquarium. Remove this fish as soon as you can and treat it in a quarantine tank! If the fish is eating, treat its food with an antibiotic. If not, treat the tank water with a strong antibiotic and hope for the best. If dropsy isn't caught in its early stages (lethargy, swollen abdomen, swimming in a bizarre manner) it is almost always fatal.

Swim Bladder Disease

This is an infection of the swim bladder, and it causes fish to swim upside down, sideways, all sorts of unusual ways. In goldfish, often times something in their diet will make them swim funny for a short time until their dinner is digested. If this seems to be the case, switch foods! For a more in-depth article on Swim Bladder Disease, visit Frank Indiviglio's article on That Fish Blog.

Visit That Fish Blog for more information on other Common Fish Diseases and Conditions.