Goldfish fungus: Types of fungus, causes and treatments

The fungus grows on fish due to less than ideal water conditions and is the most common disease in fish. It appears as cotton-like growths on the gills, mouth, and face.

Fungal infections are usually caused by an injury to the fish’s skin or an underlying disease such as parasites or bacteria. Broken skin can also occur due to sharp edges in the aquarium or fights. If she fights, then it is imperative to bring out the aggressor fish. If not treated promptly and appropriately, the fungus can infect the fish’s internal organs and cause death.

There are several types of fungus, each requiring a slightly different treatment.

Stress and a lowered immune system will cause the fungus to grow more.

Various types of fungus

Saprolegnia fungus

Saprolegnia the fungus infects fish and their eggs. This fungus will attack the internal organs and deeper tissues of the fish. It looks like a light gray cottony growth on the skin, fins, gills and eyes.

This type of fungus appears as a secondary infection, usually affecting sick or injured fish. This fungus loves to eat dead material in the aquarium, and the more detritus it has, the more this fungus will float around.

Keeping the aquarium clean and maintaining the water regularly will help reduce fungi and keep the fish healthy.

If you suspect this is the cause of the fungal growth, it should be diagnosed by an aquatic veterinarian. This fungus does not respond to antibiotics, so treating the underlying problem is the best way to treat it.

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cotton fin fungus

Cotton fin fungus, also known as cotton fin disease. This fungus takes over sick or injured fish. It manifests itself in the form of cottony growths on the body wherever there is an injury or open wound. This open wound allows the fungus to grow better and, if left untreated, can lead to health problems or death.

This fungus can also occur along with a bacterium known as fin rot, which can be caused by the same flavobacteria bacteria. Fin rot appears as frayed edges of the fins. Cotton fin fungus is treated by veterinary diagnosis and can be treated in the whole tank or by injection. It is imperative that sick fish be quarantined during treatment and recovery so that they can recover properly.

egg fungus

Egg fungus is commonly found in breeding tanks and grows on infertile eggs and quickly spreads to other healthy eggs. Once the fungus begins to spread, it will gradually kill all the eggs.

Removing affected eggs is one way to treat the infection, however this can be difficult to achieve.

Once the eggs have been removed from the main tank and transferred to the setter tank, you can rinse them in clean water to remove any potential disease from the main tank that could harm the eggs and place them in a new tank. Metaline blue is sometimes added to prevent fungal growth, but sometimes this is not necessary. A quick rinse, proper aeration and clean water are usually all that is needed to keep eggs healthy.

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fungus treatment

The first thing to do when treating a fungal infection is to move the affected fish to a separate enclosure or quarantine tank to ensure that uninfected fish do not receive treatment or suffer from treatment.

Fungus treatment depends on the type of fungus that affects your fish.

Saprolegnia I treated by treating the water with potassium permanganate. Fungal infections should begin to clear up or be cured within two weeks of treatment and consistently clean water.

Vata disease is treated with an antifungal supplement to the water where the diseased fish are kept. You can also increase the salt content of the water, but be careful not to overdo it as this can also hurt the fish if too much is added.

You should always consult your veterinarian before starting treatment for any potential medical condition. The veterinarian will prescribe the appropriate treatment and be sure to follow the instructions.

How to Prevent Fungal Infections

The best way to prevent fungal infections is to keep the water in your aquarium or pond clean at all times. If there are any aggressive fish feeding on others, then the aggressors must be removed to prevent further damage to non-aggressive fish.

Clean water is essential to prevent any disease and is good aquarium care. Make sure all your water conditions are suitable and maintained within the normal range for the fish you are keeping.

It is easier to prevent the fungus than to treat and potentially deprive the fish. Clean water means healthy fish.

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Fungal infections occur due to unsuitable water conditions and sick or injured fish. Maintaining water conditions and providing healthy living conditions will help keep fish in good condition to better fight disease.

There are three fungal infections that are well known and should be diagnosed by a veterinarian and given appropriate antibiotics.


  • Saprolegnia
  • cotton fin fungus
  • egg fungus

The fungus is usually seen as a secondary disease because when the fish is in an unhealthy state, the fungus can take root better. Bacteria, parasites, and damaged skin are some common reasons fungus gets out of control.

The best way to prevent the spread of fungus is to keep your aquarium clean and well maintained. If there are aggressive fish in the aquarium, they will need to be removed immediately to prevent further damage to other fish. It is always better to prevent a disease than to try to treat it and risk losing your fish.

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