How to Cure Fungus On Aquarium Fish


How to Cure Fungus on Aquarium Fish

If your fish has a white- or gray-colored growth on its mouth or body (often with a fluffy texture like cotton), it could have a fungal infection. Fungal infections can be caused by poor water quality or stress. They can quickly lead to secondary diseases so it is crucial to take action immediately. In this article, we cover several options for treating fungus, as well as how to stop it from coming back.

We recommend that any signs or symptoms of illness are immediately addressed by a professional. We want to make sure the fish’s environment is optimal and free of any stress factors before we start treatment. Clean the glass to see the condition of the fish. Next, use a siphon or vacuum to change the water and vacuum the substrate. (Read this article for a step-by-step guide on how to clean an aquarium.)

Fungus is often preventable, so the next step is to find the cause of the infection. There’s no point in treating the fish if we don’t stop the source of the problem because then the fungus may come back again in full force.

What Causes Fungus in Fish?

Fungal infections are often caused by poor water conditions. This is why we see so many betta fish suffering from this disease. They are often kept in small containers that have no heaters or filters. Bettas thrive at temperatures of 78-80 degrees Fahrenheit, so they will need a heater to keep them warm in rooms that are below this temperature. To prevent their waste from rapidly fouling the water, you should keep them in an aquarium with at least 5 gallons. Regular water changes, especially floating ones, are good ways to get rid of toxic waste before it affects your betta’s well-being.

Nutrient deficiencies can be another reason why fish get fungus. To be healthy, fish, just like humans, require a balanced diet. Feeding fish from the same jar of flakes all the time is like feeding a person only hamburgers every day. Although they may be able to survive, their bodies are likely not in the best of health. You should ensure that your pets have access to a variety of food so they can get all the nutrients they need and that you provide them with high-quality, fresh foods. Although the expiration date may indicate that the food will be good for three more years, air and moisture can get into the containers, which can cause the food to go bad in just a few months. Splitting the fish into smaller bags can help preserve freshness. Avoid using your fingers to lift food from the container. This can cause mold and other diseases.

Feed your fish a variety of high-quality foods to make sure they get all the vital nutrients to boost their immune systems.

Many livebearers, including fancy guppies or mollies, get fungal infections very quickly after being brought home from the pet shop. We have a whole article that dives into why livebearers in the aquarium industry are no longer as hardy, but essentially these fish are mass-bred in countries where fresh water is expensive to come by. Therefore, it is more cost-effective to raise them in both fresh and saltwater. When your guppies have been raised in brackish water for their entire lives and then suddenly get dropped into a purely freshwater environment, they’re often left in a very weakened state that makes them susceptible to foreign pathogens like fungus spores.

Bottom line: aim to eliminate as many stress sources as possible. Reduce bullying and aggression in African cichlids. Keep the gravel clean for bottom dwellers and the water quality for sensitive species high. Avoid keeping shy fish near bright TVs, bright lights, moving shadows, and high-traffic areas of your home. You might consider moving elderly animals with weaker immune systems to a “retirement” tank that has less competition and more activity.

How do you get rid of fungus on fish?

Maracyn can be used to treat fungus or rot in the mouth of fish. Certain bacterial infections (such as columnaris) look like cottony growths or grayish-white patches around the mouth and thus should be treated with an antibiotic. Clean the aquarium thoroughly and get rid of any chemical filtration such as activated carbon or Purigen. Follow the instructions listed by the manufacturer by dosing 1 packet per 10 gallons of water and repeating every 24 hours for 5 days. Even if symptoms appear to have disappeared, you must continue with the 5-day treatment.

Maracyn and IchX may be used if the fungus has spread to other parts of the fish’s bodies. Ich-X is a combination of formaldehyde and methanol that are effective against fungal infections. Before treatment, clean the aquarium and remove any chemical filtration. If the fungal infection is minor, dose 1 packet of Maracyn and 1 tsp of Ich-X per 10 gallons of water at the same time. Let the medication sit for one week to ensure that all symptoms disappear. You can use 1 packet Maracyn with 1 tsp Ich-X for 10 gallons of clean water. Repeat the process every 24 hours for five days.

Salt is an excellent way to treat mouth and body fungus if you don’t own a planted aquarium. You can use any form of regular salt made of sodium chloride (NaCl), but for the purposes of this article, we’re using aquarium salt or rock salt – not table salt, marine salt, or Epsom salt.


After many years of using salt for medicinal purposes, we have found that most tetras, barbs, danios, African cichlids, livebearers, betta fish, goldfish, shrimp, and even plecos are tolerant of salt. Anchor catfish, for example, are sensitive to salt and should not be exposed. You can make sure that your fish are able to withstand the salt treatment by using a low salt concentration, 1 tablespoon per 3 gallons. If the fish is healed after one week, gradually remove the salt via a series of weekly 30% water changes. If the fungus is still active, you’ll need to increase the salt concentration. For detailed instructions on how to do this, please continue reading our full article on salt dosing. For a powerful combination against the fungus, you can use salt with IchX.

Are there any other fungal remedies that work?

We have found that herbal remedies are not effective against fungal infection. For fish that have been infected, stronger medication is required to save their lives. After years of managing a fish market and helping hundreds upon hundreds of customers, Maracyn and Ich-X are the only treatments that have proven effective against fish fungus.

Fungal spores can be found in aquariums but they are often preventable. It is important to improve your fish’s health, provide them with the right environment and nutrients to fight off any fungal spores.

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