Goldfish Fungus Disease Treatment

Goldfish Fungus Disease Treatment

Fungus disease, otherwise known as the cotton wool disease, is a widespread disease in the aquarium, particularly among goldfish. The bad news here is that goldfish are susceptible to fungus infection, but the good news is that fungus does not affect healthy fish. This variation is because fish have a weak immune system when they are living under poor conditions.

Treatment of fungal disease in goldfish includes bathing the fish with freshwater aquarium salt or commercially available antifungal therapies that are suitable for aquarium use. You can also add either aquarium salt, methylene blue to the water as a preventive measure in the general tank. You can also bathe the affected fish in a portion of copper sulfate.

The first line of action is to isolate affected fish and keep them in a separate tank. Remove all chemicals from your filter, particularly activated carbon. It is also advisable to treat the fungal infection as soon as possible before it gets so life-threatening. If you don’t address the disease on time, it will spread from the skin to the muscle tissue of the fish; consequently, the fish will die off.

Causes Of Fungus Disease In Goldfish

As much as goldfish is prone to be infected with fungus parasites, healthy fish are quite safe. Fish with a weak immune system or those kept in water with poor quality will also easily contract the fungus. Likewise, fish with already compromised health like those with parasitic ulcers and open wounds are also susceptible.

Goldfish fungus is prevalent in almost all air and water because of the nature of its spores. Once it finds its way from the body of the fish into the tissues, it can cause dehydration, suffocation, blood poisoning, and eventual death.

Branchiomyces usually cause fungus disease in goldfish. Branchiomyces is an aggressive and ruthless fungus that kills fish by damaging the gill tissue. The affected areas on the gills allow a hole in the gill membrane because they slough off. The presence of these holes in the gills membrane will eventually make the fish suffocate.

Branchiomyces thrive better under high water temperature, high levels of organic waste in water, high nitrate levels, and overcrowded tanks. This fungus is also prevalent during the summertime because of the higher temperature of the tank during this time.

Symptoms Of Fungus Disease In Goldfish

It is best to recognize the presence of fungus invasion in your tank before the effect on the fish gets too extreme. Fungus disease in goldfish can give visible signs before it fully manifests itself in the fish. Although some non-fungus condition presents symptoms that are slightly like that of fungi, they are usually distinguishable.

In the early growth stage of fungus of the body and fins of fish, the fungus will appear like cotton. This cottony growth is often prevalent in areas like fin, skin, gills, and eyes. Real fungus disease is often unmistakable because they look like a bunch of cotton. They also have characteristic hairy tendrils that stick out of them.

Once you notice that the fish is uncomfortable in the tank and the discomfort can be together with the loss of appetite, it might also be a sign of fungal infection. Nevertheless, you cannot entirely detect fungi infection in fish.

Prevention Of Fungal Disease In Goldfish

First off, the full manifestation of fungal infection in your aquarium is unlikely if you have a clean tank. Fungi cannot invade the system of a healthy fish; dirty tanks and poor water makes your fish sick and also compromises their immune system.

A dirty and overcrowded tank makes your fish susceptible to fungus invasion in two ways; first, the dirty tank condition favors the growth of fungus. Second, ammonia and other organic matter from rotten fish waste can cause the slim protective layer of the fish to wear out. Likewise, these chemicals can cause burns on the body of the fish.

This chemical burn opens up the skin of the fish to allow easy access by the fungi. Overcrowded tank means more waste, more bullying, more stress for the fish, and less hiding place for them. Stress from the overcrowded tank alone can reduce the ability of fish to recover from wounds. It can also affect their inner strength to fight off infection.

The first line of defense against fungal infection in the tank is to ensure the aquarium tank is clean and the water parameters are at top quality. It is also essential to ensure that your aquarium tank is spacious enough to give room from each fish. However, if you find out your fish have a fungal infection, it is best to treat it immediately.

Treatment Of Fungal Disease In Goldfish

Aquarium salt bathing is the most recommended treatment for fungal infection. It is most effective if you add 3 tablespoons of aquarium salt per 1 gallon of water. You must ensure that the salt you are using is not iodized.

The use of fish drugs like malachite green, methylene blue, fulvinex, and the use of potassium permanganate are also usually recommended. These compounds will work best when you use them according to manufacturer’s instructions and avoid overdosing them.

Similarly, these compounds are all capable of killing aquarium plants and snails; so, you should isolate the affected fish for treatment. Likewise, most of the chemicals used for the treatment of fungal infections are relatively toxic. Therefore, it is essential to use with caution.


Goldfish are one of the aquarium fish that are highly prone to fungal infection. However, you can mitigate the susceptibility of goldfish if they are healthy, less stressed and if they are living in the water of good quality. Overall, fungi find it hard to thrive in clean water, and also find it hard to establish and manifest itself in healthy goldfish.

Fungi infection of goldfish can become life-threatening and cause eventual death if you don’t take swift action steps early enough.

The treatment of fungal disease often starts with isolation of the affected fish, cleaning, and decongestion of the tank. You can treat the affected fish afterward with the use of aquarium salt and other antifungal chemicals that are mostly available commercially.


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