Anemia in Fish

By PetMD Editorial on Jul. 18, 2008

Anemia is a heart and blood vessel condition which is recognized by the low number of red blood cells found in the animal. It can affect many types of fishes, so be observant of your pet and take your animal to the veterinarian if anemia is suspected.

Symptoms and Types

The most common symptom -- which is also quite visible -- is abnormally pale gills in your fish.


Fishes can have anemia due to many reasons; among them:

  • Bacterial, fungal, viral and parasitic infections
  • Folic acid deficiency (especially prevalent in channel catfish)
  • Exposure to high levels of nitrites – found in the water – for an extended period of time
  • An infestation of blood-sucking parasites (i.e., leeches)

The blood that is drained by the leeches causes anemia in fishes. They can also introduce other parasites into the fish's blood stream. Usually, aquariums and fishponds become infested with leeches because there is an infected plant or animal in the environment.


Anemia is not very common in fishes. When it does occur, however, the veterinarian will seek to treat the underlying cause of the condition. For example, increasing folic acid in the fish's diet can resolve anemia do to a deficiency in the substance. Anemia due to infections and parasitic infestation, on the other hand, are treated with medications for the infection, followed by a thorough cleaning of the fish's environment (i.e., aquarium, pond). If necessary, the infected fish may be quarantined until all traces of the leeches and its larvae and eggs are gone. Water should also be tested regularly to keep nitrite levels correct.

Help us make PetMD better

Was this article helpful?

Get Instant Vet Help Via Chat or Video. Connect with a Vet. Chewy Health