Goldfish Fungus

Identifying and Treating Goldfish Fungus

You are best off thinking of goldfish fungus not as a disease in itself but as the symptom of other underlying causes.  Goldfish fungus rarely occurs by itself in an otherwise perfectly maintained tank.  The type of fungal disease most common to goldfish is an opportunistic condition that almost always piggybacks on some other condition.

Tank Maintenance

By far the deciding factor when it comes to whether or not your goldfish will be vulnerable to fungal disease has to do with the overall maintenance of your tank.  If you keep to a schedule of changing your tank regularly and avoid build up of waste, you can sidestep the conditions that contribute to goldfish fungus.  You should try to change a quarter to a third of your goldfish tank every week in order to avoid the build up of bacteria.  Make sure that you dechlorinate the tap water before you add it to the tank.  Some smaller tanks may need more attention.

In addition, you should be sure never to clean your tank using Windex or any other kinds of chemicals.  A simple hot water cleansing will do the job when cleaning the whole fish tank.  Furthermore, make sure that you do not keep your tank in the direct sunlight or over some sort of heating device that will drive the water temperatures above 70 degrees.  Goldfish show little tolerance for the higher temperatures in the aquarium spectrum.  (On the other hand, so long as not asked to adapt too quickly to changing temperatures, goldfish show quite a healthy hardiness when it comes to colder more severe goldfish climates.)

Conditions that Typically Accompany Goldfish Fungus

Even if your tank has the conditions that make fungus a greater possibility, often your goldfish will not manifest any signs of fungus.  This is because fungus needs the right opportunity in order to establish a foothold on your goldfish.

One of the most common causes of fungal infection in fish is injury.  Often a fungus will get its foothold after another fish has spent some time picking at a particular goldfish.  The wounded fish will develop white circles near the spot of the wound and will start to suffer from inflammation around that area.  Typically, other fish will continue to pick at the wounded fish in a grotesque torture.

Even single fish may injure themselves, however.  This typically occurs when there is a sharp object located somewhere in the tank.

Injury however, is not the only way that a goldfish may become vulnerable to infection by a fungus.  Parasites and diseases may also lead to an overall weakening of a goldfish’s immune system, making it vulnerable to fungal disease.


In order to get rid of your aquarium’s fungal disease, you will have to purchase an antifungal solution at your pet store.  If you have a fish that is particularly bad off and you have the wherewithal to do so, you may also try to quarantine this fish into his own tank with a purified salt treatment so that he stands that best chance of recovery (make sure you do not use regular salt; it contains iodine).  The prognosis is still not very good, but this may give the individual fish the best shot (although it is likely a long shot) at recovery.

Cotton Wool Disease

If the anti-fungal treatment seems to have no effect, there is a chance that your goldfish may actually be suffering from a bacterial infection known as cotton wool disease.  If this is the case, then you will want to take appropriate measures to treat this disease.