Betta Fungal Infection (White Fungus): Symptoms, Treatment, Prevention

betta fungal infection symptoms treatment
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Betta fish are getting increasingly popular among aquarists due to their beautiful colours and attractive look.

However, it’s also true that they’re extremely sensitive to even minor changes in their living environment, making them prone to various health conditions.

Fungal infection is one of the common health conditions betta fish may encounter during their lifecycle.

It can lead to serious health problems in your betta fish unless you treat it in the early stages.

This article is a guide on fungus, explaining its causes, symptoms, and treatments in detail so you can take good care of your bettas to keep them safe from this lethal disease.

What is betta fish fungus?

Betta fish fungus, also called “betta fungus,” refers to the fungal infection in betta fish.

Many different species of fungi can cause infection in betta, but the most common one is Saprolegnia.

Although the mortality rate in betta fish due to fungus is relatively lower than in other diseases, the chances of your betta’s survival may become slim if you leave this condition unchecked for longer.

Some aquarists confuse “betta fish fungus” with “betta fin rot”, while these are different health conditions.

Both fungal and bacterial infections can cause betta fin rot.

On the other hand, betta fish fungus results from only fungal infection.

What are the causes of betta fish fungus?

Betta fish fungus is also known as mycosis.

The fungi species that cause mycosis are always present in the aquarium but only attack when your betta’s immune system is not strong enough to fight them off.

So, anything that weakens or compromises the immune system can go down as the cause of mycosis.

Your betta may also lose immunity against fungal infection after getting severely ill due to other diseases.

Following are some common causes that can trigger weakness in your betta fish:

  • Poor water conditions

Betta fish love to live in a clean, well-maintained environment where they can easily roam around and play.

If your fish tank is dirty or contains high levels of ammonia or nitrites, it can weaken their immune system by causing them to become stressed out.

A stressed betta is more susceptible to fungal infection than a healthy one.

  • Improper water parameters

Water temperature and pH levels that don’t suit your betta can trigger stress.

This range will depend on the species of your betta, but always keep in mind that betta fish are hypersensitive to changes in the environment.

So even a minor change in temperature or pH level can cause them to become stressed out.

  • Overcrowding

If your aquarium is overcrowded, the levels of wastes, such as ammonia and food leftovers, will be higher in the water, triggering stress in your bettas.

The aquarium should be large enough to provide bettas with adequate space to swim, hide, and explore.

Adding more fish in the aquarium means a higher bioload that lowers the water quality and increases the risk of fungal infection.

  • Stress

Stress in betta fish results from poor water conditions, sudden changes in water temperature and pH, and lack of free space in the aquarium.

Besides these factors, aggressive tankmates can cause your betta to become stressed.

The lack of decorations and live plants in the aquarium might also be the reason for stress as it causes boredom in betta fish.

Betta owners must provide smooth and playful decorations in the fish tank to avoid boredom and keep them active.

  • Physical injury (trauma)

Areas of your betta’s body affected by a physical injury or trauma provide an anchor point for fungal infection.

Fungus attaches itself to these areas more easily than healthy ones, getting an easy entry into the fish’s body to cause infection.

Physical injuries in bettas can result from fighting with an aggressive tankmate or striking with a sharp object (like sharp or rough decoration) in the aquarium.

  • Poor (Unbalanced) Diet

An unbalanced, low-quality diet can weaken your betta’s immune system, putting them at risk of developing a fungal infection.

Such a diet lacks several essential nutrients and minerals necessary for the immune system to work at its maximum capacity.

You should choose a high-quality, balanced diet as it can help them keep their bettas’ immunity at the highest level.

  • Genetically weak immune system

If your betta’s immune system is genetically weak, there’s nothing much you can do to keep them safe from fungal infection.

The likelihood of developing a fungal infection in such bettas is relatively higher than in the ones with normal immune systems.

Symptoms of betta fish fungus

Following are some significant symptoms you may notice in your bettas if they’re suffering from mycosis:

  • White fungus growth

White fungus growth is the most noticeable symptom of fungal infection in betta fish.

On the onset of mycosis, you may start noticing a cottony or fluffy white or greyish growth on the fins and tail of your betta.

As the infection progresses, the growth may start spreading to other areas of the body.

Some betta owners confuse mycosis with other health conditions involving fungus growth, such as columnaris.

However, mycosis can be easily distinguished from these conditions by a closer inspection of the shape and texture of the fungus growth.

In betta fungus, the shape of fungus growth is hair-like, while in columnaris, it looks like a cotton ball.

Ich is another condition that can be confused with mycosis due to the appearance of white spots in different areas of the fish’s body.

One may take these spots as fungus growths, but they’re just cysts filled with parasites.

  • Body discolouration

If your betta suffers from mycosis, you may notice discolouration in different body areas, especially fins, and tail.

The fish’s body colour becomes darker or lighter than usual, depending on the severity of the infection.

  • Ragged or frayed fins

The fungal infection may cause your betta’s fins to become ragged or frayed.

You may also notice damaged or torn fin areas when the mycosis worsens.

  • Lethargic behaviour

The betta suffering from fungal infection may show temporary inactivity and lack of energy.

They may appear lethargic under severe attack of mycosis.

In such conditions, betta fish may stick to a decoration or live plant in the aquarium and remain there for extended periods.

  • Loss of appetite

Bettas with mycosis may lose their appetite temporarily or permanently or show less interest in eating.

If loss of appetite prolongs, they may develop emaciation (abnormally thin and weak body).

  • Unusual swimming pattern

If your betta is swimming abnormally, like upside down or sideways, it might be due to a fungal infection.

Bettas with mycosis may start swimming upside down on the water’s surface.

  • Fin loss

If mycosis is left untreated, the condition can reach its severe stage, causing fin loss in betta fish.

Besides these symptoms, you may notice scaly patches and spots on different body areas of your betta.

It’s important to remember that all these symptoms, except fungus growth, can also be caused by other health conditions in betta fish.

Therefore, fungus growth is a clear indication of mycosis.

So, if you notice all of the above symptoms, including fungus growth in your bettas, it’s likely that they’re suffering from a fungal infection.

However, if you don’t notice fungus growth but all other symptoms are present, you should diagnose thoroughly before reaching any conclusion.

How to treat fungal infections in betta fish

Fungal infection in betta fish is a treatable disease, especially if you know its exact cause.

Aquarists use various treatment methods to deal with betta fish fungi, such as the use of antifungal medication, Indian almond leaves, and allopathic medications.

No matter the treatment you use, the first thing you need to do is to isolate sick bettas from healthy ones to avoid the spread of disease.

For that, you can prepare a quarantine tank filled with clean water having the same temperature and pH level as the main aquarium.

Transfer your betta fish to the quarantine tank and start treating them.

Following are some popular treatments for betta fish fungus:

  • Antifungal Medications (Drug therapy)

Fungal infection can be treated with a wide range of medications available in the market, including Methylene blue and Pimafix.

Follow the instructions on the label on how to treat fungal infections.

  • Indian almond leaves treatment

Indian almond leaves, also known as Catappa leaves, are believed to be a rich source of antifungal organic compounds. They contain tannic acid that can kill fungi.

Researchers believe Indian almond leaves contain a high quantity of propranolol that helps betta’s immune system fight off fungal infection.

You can directly add Indian almond leaves cut into small pieces to the aquarium water. The quantity of leaves you should add depends on the size of your aquarium.

  • Allopathic medications

Some allopathic antifungal medications, such as KanaPlex and Maracyn, are effective against fungal infections.

So, you can use these medications to treat your bettas suffering from fungal infection.

  • Aquarium salt treatment

Aquarium salt is an excellent choice to strengthen the immune system of your betta fish, so they can fight fungal infection at their maximum capacity.

You can directly mix an optimum amount of aquarium salt in the fish tank or treat your sick bettas with it in your quarantine tank.

Here is our guide to using aquarium salt.

Preventing betta fish fungus

Prevention is always better than treatment, especially when it comes to conditions like fungal infection.

Following are some useful preventative measures that you can take to prevent betta fish fungus from happening in the first place:

  • Keep your fish tank clean: Poor water conditions are one of the root causes of fungal infection in betta fish. You can improve the water quality in your aquarium by keeping it clean. Regular water changes can help keep the fish tank clean and prevent fungal infection.
  • Avoid overfeeding: Overfeeding your betta fish results in food leftovers in the aquarium that pollute the water when it decays. Therefore, you should always avoid overfeeding to maintain your water quality.
  • Don’t overcrowd the aquarium: Overcrowding can lead to increased stress, poor water quality, and a high risk of fungal infection in betta. Therefore, you must keep the number of inhabitants to a minimum in the aquarium.
  • Quarantine new fish before adding them to the aquarium: New fish should be quarantined for at least 15 days before adding them to the main aquarium.
  • Feed a balanced diet to your bettas.


Betta fish fungus is a common disease characterised by white fungus growth on the fish’s body, causing a loss of appetite, body discolouration, and loss of fins.

Poor water quality, stress, and an unbalanced diet are some significant causes of this disease.

You can keep your betta fish safe from fungal infection by taking the above-mentioned preventative measures.

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