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Home > Goldfish > Goldfish Fungus Diseases: Symptoms, Treatment & Prevention Guide

Goldfish Fungus Diseases: Symptoms, Treatment & Prevention Guide

Scales loss on back of sick lionhead goldfish

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Dr. Paola Cuevas

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Goldfish are susceptible to a range of different diseases that can become fatal if they are not treated, with some of the most common diseases spawning from a type of fungus. There are fungal spores naturally present in the water column of an aquarium, but they can affect goldfish that are vulnerable due to open wounds, stress, or poor water quality.

It is important to learn about the most common fungal diseases that can affect your goldfish so that you know how to recognize the symptoms. This article will explain the different types of fungal diseases and how you can effectively diagnose, treat, and prevent them from occurring in your goldfish.


The 4 Common Goldfish Fungus Diseases

1. Gill Rot (Branchiomyces)

This type of fungus causes the gills of a goldfish to rot away. It can become fatal if not treated promptly because your goldfish relies on their gills to breathe normally.

  • Grey and mottled gills
  • Respiratory distress
  • Torn and damaged gills
  • Rapid breathing
  • Treatment: Unfortunately there is no established treatment for this disease as it has a high mortality rate. Clotrimazole, copper sulfate, and formalin have been used for treatment with some success. In severe cases, euthanasia may be a kinder method for a goldfish suffering from this fungus disease. It is important to increase the amount of oxygen in the aquarium by using an aeration system so that the infected goldfish do not have to gasp at the surface to breathe easier.
  • Prevention: This fungus thrives in a warm environment, so you may want to gradually lower the temperature in your goldfish aquarium during treatment. Unfortunately, gill rot is usually fatal in goldfish and prevention is better than treatment. If you notice that your goldfish has damage to their gills, it’s important to keep the aquarium conditions sanitary to prevent this fungal spore from attacking the damaged gills.

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Sick goldfish lying in the bottom
Image By: mrk3PHOTO, Shutterstock

2. White Fungus (Saprolegnia)

Also known as “cotton wool disease” this fungus causes fluffy white growths on your goldfish’s body. It eats away at their slimy coating which then leaves the goldfish’s body vulnerable to infection.

  • Raised pale scales
  • White fluffy growths across the body
  • Slime trailing off the goldfish
  • Rapid breathing
  • Lethargy
  • White growths on the mouth
  • Treatment: A salt bath or dip every couple of hours is recommended to treat mild cases of white fungus disease. It is important to keep the goldfish in a treatment tank isolated from other goldfish as this disease is highly contagious. For more severe cases, methylene blue baths or machalite green dips can be effective at killing off this fungus. Pimafix has proven to be an effective treatment against white fungus disease.
  • Prevention: Gradually lower the temperature in the aquarium and ensure that you do regular water changes to improve the quality of the water. Avoid handling your goldfish or placing dirty hands and equipment into the water column.

3. Ichthyosporidium

This is an internal fungal infection that affects a goldfish’s liver and kidneys before it spreads externally. This makes it difficult to treat this disease in the early stages because most goldfish will not show symptoms until the disease has progressed.

  • Sluggish behavior
  • Loss of balance
  • Dull coloration
  • Loss of appetite
  • Weight loss
  • Hollow belly
  • Cysts
  • Treatment: It is difficult to treat this fungal disease in its advanced stages, but if you are lucky enough to treat your fish for this disease while the fungus is still internal, then there is a higher recovery rate. Your goldfish will need to be placed on the medication used to treat internal fungal and bacterial infections. The cysts and body sores can be treated using a salt bath. The medication can be introduced into your goldfish’s body by soaking it into their food.
  • Prevention: This fungal disease is difficult to prevent but ensuring that your goldfish are kept as stress-free as possible is important. Keep the water temperature lowered to prevent the spores from multiplying and avoid handling your goldfish’s food with dirty hands.
sick goldfish swims upside down
Image By: M-Production, Shutterstock

4. Ulceration Disease (Achlya)

Most commonly caused by poor water quality, ulceration disease is a fairly common fungoid that affects goldfish. This disease is highly contagious, and all the aquarium inhabitants should be treated even if you notice that only one fish is infected.

  • White film over the eyes
  • Swollen gills
  • Respiratory distress
  • Lethargy
  • Slimy film covering the body
  • Treatment: If your goldfish is in the early stages of this disease, salt baths will help to kill off and prevent the fungal spores from multiplying. More advanced cases will require a stronger medication like malachite green or methylene blue dips to combat the damage this fungus can cause. You can also use medications with copper sulfate but be sure to follow the correct dosage on the bottle of the medication.
  • Prevention: Keep the goldfish aquarium clean and ensure that there is plenty of water movement from a filtration system. A warm and stagnant aquarium can be a breeding ground for this type of fungus. Regular water changes will also help to improve the quality of the water.



Fortunately, most goldfish fungal diseases are treatable. If you suspect that your goldfish might be suffering from a type of fungus, you must begin the correct treatment right away so that they have a better chance of recovery. By practicing good aquarium hygiene methods and keeping your goldfish stress-free, you will be able to help prevent the most common fungal diseases from affecting your goldfish.

Featured Image Credit: Zay Nyi Nyi_Shutterstock

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