Treating Fish Fungus

Fish FungusHow to Treat Fish Fungus

Fish fungus is most commonly found in outdoor freshwater ponds that have an overabundance of decaying organic matter. However, it can also be found in home aquariums. It is very easy to detect a fungal infection because the fish will have a fluffy coating on its body that resembles wool. This coating can be either white or grey in color.

The good news is that typically, fish fungus only attacks the external organs of the fish, but in rare cases, it can affect some of the fish’s internal organs. This does not mean, however, that immediate attention is not necessary. If proper treatment is not received, a fungal infection can lead to death.

Only Effects Unhealthy or Stressed Fish

A fungal infection is considered to be a secondary condition because it only occurs in fish that are either injured, ill, or stressed. Healthy fish have a layer of mucus coating their skin that protects them from this type of infection. However, if this mucus has been damaged or if the fish’s immune system has been compromised, this mucus shield will not protect them.

Various stress factors, such as poor water conditions, malnutrition, overcrowded, dramatic change in water temperature, or a chemical imbalance will reduce the fish’s immune system and make them susceptible to fungal infections. This fungus can spread very rapidly and may affect more than one fish at a time.

Treatment Is Required

It is recommended that you treat the entire tank with malachite green. This will protect all the fish in the aquarium or pond. Once the treatment has been completed, you should remove the infected fish and house it in a quarantine tank. The infected fish can also be treated with salt baths, but it should not be released back into the regular tank or pond until all signs of the infection are gone. If any other type of infection is detected, you can use an antibiotic to help the fish heal faster. Interpet have an excellent Anti Fungus Solution which can help.

Slowly increase the water temperature of both the regular tank or pond and the quarantine tank, until it is about 76°F. Fungus does not grow well under warmer conditions, so increasing the temperature will stop this growth. Once the infection is gone, you can slowly return the water to its original levels. Be careful to increase or decrease the temperature over several hours, so you do not add unnecessary stress to the fish.


While fungus is a common problem found in both ponds and aquarium, it should not become a reoccurring issue. If you are having a repetitive problem with fungus, then there is likely a problem with your tank, such as overcrowding, poor water quality, or unclean conditions. You will need to identify the problems and take effective action, or the fungus will continue to attack your fish.

Since fungus is easy to detect, treatment should begin almost immediately. It may take several days or weeks until you can return the quarantined fish back into its regular home. As long as the water conditions are improved and the fungus is removed correctly, it should not reoccur.