Betta Fish Fin Rot & Tail Rot: Symptoms, Treatment, Prevention

betta fish fin rot tail rot treatment
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The sudden, scary attack of fin rot can put betta fish owners into a panic, despite it being a common disease in betta fish.

The good news is that betta fish with fin rot can be easily treated; especially if detected early enough.

We’re going to discuss standard preventive measures in the last section of this article, which we can also use to prevent betta fish fin rot and tail rot.

Keep reading to find out everything you need to know about fin rot in betta fish, what it is, its symptoms, causes, and how to cure it in your freshwater aquarium!

What is betta fish fin rot?

Fin rot is a common disease in betta fish, which is caused by a bacterial and fungal infection.

In case of bacterial infection, gram-negative Aeromonas sp., Pseudomonas sp., and Vibrio sp. bacteria are responsible for fin rot.

These bacteria attack the betta’s fins and begin to eat them, and eventually deteriorate them.

Bettas purchased from large box stores are more susceptible to bacterial infection because it’s highly likely that they may have fin rot already before you transfer them to your freshwater aquarium.

Under-attack fins show white, red, or black edges as signs of deterioration.

Fungal infections have the same mechanism of action as bacterial infections. In bettas, fin rot can be caused by a variety of fungal species.

Fin rot shouldn’t be confused with other fin damaging conditions, such as fin biting, tearing, or splitting.

These damages are due to physical injuries resulting from fighting and striking aquarium walls.

What causes fin rot and tail rot in betta fish?

The following are the common causes of fin rot and tail rot in betta fish:

  • Dirty Aquarium

The freshwater in your aquarium is usually rich in all forms of life, including bacteria, fungi, and other microorganisms.

In most cases, betta fish are immune to these microorganisms because their immune system is capable enough to fight against them.

However, a dirty aquarium, such as having cloudy water (usually by bacterial bloom), uneaten food, uncleared faeces, and decaying plants can develop stress among betta fish that causes the weakening of their immune system.

With a weak immune system, betta fish become susceptible to fungal and bacterial attacks.

You should need to be concerned if your tank water is cloudy, full of uneaten food, have globs of faeces, and have dying plants.

Clearing these maintains good water that prevents fungal or bacterial infection.

  • Poor Water Parameters

Poor water parameters are another cause of fin rot in betta fish – in fact, it’s closely linked with a dirty aquarium.

In a dirty aquarium, the detritus in the tank will decompose to form ammonia. This is then converted to nitrite and nitrates via the nitrogen cycle.

If your aquarium has high ammonia, nitrite, and nitrate levels, your newly bought betta fish can develop the new tank syndrome that can compromise the abilities of their immune system.

Therefore, you must ensure that your water tank is properly cycled and has the ideal water chemistry (pH levels, water hardness) before transferring new betta fish (or any fish) into it.

A betta’s immune system can be weakened by poor water parameters, which can lead to fungal and bacterial infections.

Thus, make sure to understand what are the proper water conditions to keep your betta fish and always grab a test kit to measure your water parameters.

  • Improper Tank Setup

In addition to a dirty aquarium and poor water parameters, an improper tank setup is another significant reason for new tank syndrome in betta fish.

Beginner hobbyists usually have limited knowledge about betta living conditions, so they are not usually able to provide them with a suitable environment.

Many believe that the minimum size aquarium for betta fish should be 19 litres (5 gallons). This provides ample swimming space for your betta to swim around.

However, many serious hobbyists and breeders in Asia frequently keep them in smaller tanks with great success.

The key to keeping your fish alive is to have a clean aquarium with the proper water conditions needed.

Of course, if you can get a bigger tank that’ll be better.

Next, the type of gravel you’re using also has an impact on bettas. You should use sand or fine-grained gravel or aquarium soil because they don’t trap the long fins of betta fish.

Dark-coloured substrate works best as it reduces stress on your betta fish and enhances its colours.

Lastly, let’s talk about temperature.

Depending on the species of betta you’re keeping, they have different temperate requirements.

For example, the common betta splendens can be kept between 22 to 30°C (72 to 86°F).

But the betta macrostoma for example needs to be kept between 20 to 25°C (68 to 77°F) because of where it came from.

Thus, know what betta species you’re keeping, understand their natural habitat, and the according temperatures that they need to thrive in.

  • Overcrowding

If too many fish live in one tank at the same time, it can lead to overcrowding, which deteriorates water quality and increases stress in bettas which may lead to fin rot.

When there are too many fish in a tank, they fight for food, which can result in fin damage. Damaged fins are more susceptible to fin rot than healthy ones.

Besides these causes, any underlying disease or condition that can cause weakness of the immune system or stress in bettas can increase the risk of fin rot.

  • Nutritional Imbalance

A nutritional imbalance may also lead to fin and tail rot in betta fish. This could be due to the fish food you’re feeding your betta or just a lack of proper nutrition in the foods that you feed.

Bettas are carnivores in nature and require a diet with proteins and fats. So you’ll need to read the nutrition label to ensure they contain the necessary nutrition needed.

Here is a betta feeding guide I wrote that talks about what betta fish eats, how often you need to feed them, and how much you should feed them.

Take note that the causes of fin and tail rot mentioned above are not conclusive and may not lead to direct causation.

It could be a mixture of issues that stresses your betta, compromises its immune system, and thus lead to fin rot.

Symptoms of Betta Fish Fin Rot & Tail Rot

Depending on the infection stage (mild, moderate, severe), fin rot shows different symptoms in betta fish.

Fin rot can attack fins in all body areas, whether it’s the dorsal, caudal, or anal fins.

In most cases, the symptoms of bacterial and fungal fin rot are the same. The onset of fungal infection is usually followed by bacterial infection.

As mentioned earlier, white, red, and black spots along the edges of fins are one of the significant symptoms of fin rot.

Depending on the stage of infection, fin rot can show the following symptoms:

Mild Fin Rot Symptoms

Mild fin rot symptoms include brownish and jagged fin edges. Sometimes betta fish have whitish tips or spots on their fins in the mild stage of fin rot.

Moderate Fin Rot Symptoms

Moderate fin rot symptoms include:

  • Large fin deterioration
  • Fin receding
  • Bloody fin edges
  • White fuzzy growths in fins

Severe Fin Rot Symptoms

Severe fin rot has severe symptoms, such as:

  • Increased inflammation
  • Redness and swelling in the fin base
  • Bloody fin bases
  • Loss of fin membrane
  • Lethargy
  • Swimming difficulty
  • Weak immune system

If not treated, severe fin rot can cause the loss of whole fins or fin membranes.

In the severe stage, fin rot can begin to attack the body parts of bettas, especially the caudal peduncle.

Although rare, fin rot can lead to the death of infected bettas.

Stages of fin rot in betta fish

The basic difference between the three stages of fin rot is evident from their symptoms.

Here, I’ll discuss how fin rot proceeds with its action in each stage.

Mild Betta Fish Fin Rot

In the first stage of fin rot action, betta fish start showing redness and irritation at the tips of their fins in the dorsal, tail, and anal regions.

Redness and irritation will be limited and visible along the edges of the fins only.

When the mild stage reaches its peak, the fin tips look slightly frayed.

Moderate Betta Fish Fin Rot

It’s the middle stage of fin rot. One of the major symptoms of moderate fin rot in betta fish is bloody fins.

Fins may develop white fuzziness with red blotchiness in their different areas.

Under severe bacterial or fungal attacks, fins start to recede towards the body and may become tattered after a few days.

Betta fish fins show an abnormally dark colour that sometimes even gets grey.

Colour abnormality shows in especially those areas of fins that are on the verge of death. The entire area of the fins comes under significant damage.

Large rips, tears, and even hollow areas of fins due to missing chunks are visible to the naked eye.

With careful observation, you can easily figure out that these tears and rips are not caused by another fish or a physical injury.

Severe Betta Fish Fin Rot

This is the ultimate stage of fin rot. In this stage, the fin rot turns itself into body rot as it starts attacking the body parts.

Betta fish needs critical care in the severe fin rot stage. The primary symptom of severe betta fish fin rot is the onset of body decolourisation.

The betta fish’s body shows redness and sign of bleeding.

At this point of fin rot infection, a considerable number of fins may have fallen off the skin after receding, or there are only small pieces of them hanging with the body.

Treating Fin and Tail Rot in Bettas

What treatment method you use to treat fin rot depends on the stage of the disease your betta fish in.

The first and most crucial step in treating your betta fish is to organise a treatment plan.

If you’ve more than one type of fish in your water tank, the first thing you need is to set up a quarantine tank to quarantine the infected betta fish.

Although fin rot isn’t classified as a highly contagious disease, your other fish that have weak immune systems can be susceptible to developing this disease.

To quarantine your infected betta fish, you should prepare a quarantine water tank with a water volume of at least 11 to 19 litres (3 to 5 gallons).

A larger volume of water reduces the risk of overdosing on medicine and making mistakes.

This tank should already be cycled to make sure you’re providing a safe environment for your fish.

The water temperature of the quarantine tank should be similar to your freshwater aquarium from which you’re shifting betta fish.

Now you’ve quarantined your betta fish; the next step is to choose the treatment method.

There’re two types of treatment methods available for fin rot: Natural and Medication.

Natural Treatment Options

In natural treatments, you treat fin rot with natural remedies.

There’re a number of natural ways to treat fin rot, among which the most common one is to raise water quality and fix water parameters.

Before discussing it in detail, it should be noted that this treatment option is only helpful if your betta fish are experiencing mild fin rot.

Fixing Your Water Parameters

Exchanging all the water in your aquarium for fresh water all at once might feel tempting to you, but it isn’t a good way to fix water parameters and raise its quality.

Changing water at once can stress out your betta fish and even lead to bigger immune system problems.

Therefore, you must go with small water changes with a gap of a couple of days.

This way, you can replace all the water in your tank without putting your betta fish in stressful conditions.

Experts recommend replacing 20-25% of water change every couple of days.

During this process, don’t forget to regularly test water parameters to make sure they’re ideal for betta fish.

This method fixes the issue of a dirty aquarium with poor water quality. It lets your betta’s immune system strengthen to fight off fin rot.

Aquarium Salt

With regular water changes, you can also treat the tank water with aquarium salt.

Although not necessary, aquarium salt treatment is encouraged to deal with fin rot.

It is important to note that aquarium salt should be used according to the instructions printed on its label.

You may not achieve the desired results if you use too much or too little aquarium salt.

Make sure to dissolve the aquarium salt in the tank first before shifting your betta fish. Undissolved salt can harm your betta fish!

Also, make sure that you’re adjusting the proportion of aquarium salt added every time you do a water change.

Not doing so may lead you to overdosing and underdosing salt in your tank as there are still remnants of salt in the quarantine tank.

Together with aquarium salt, make sure there’s good filtration and aeration in your quarantine tanks.

You can increase aeration in your tank by using an air pump. This will increase oxygen in the water tank and promote gas exchange.

Add Tannins to Your Tank

You can consider adding tannins in your main aquarium or quarantine tank. This can be done by adding Indian Almond Leaves, alder cones, or peat.

Tannins have antibacterial and antifungal properties that help fight fin rot while reducing the stress on your betta fish.


Medicating your betta fish is an effective method to deal with fin rot in its moderate and severe stages.

It might be scary because most owners don’t want to treat their bettas with chemical medications, but it’s considered safe and helpful against extreme fin rot.

There’re many popular aquarium medications available on the market, so you’ll need to do some research.

Some of the popular medicines are Maracyn, Melafix, Aquarisol, Waterlife Myxazin, malachite green, methylene blue, or Kanaplex.

Talk to your local fish store for recommendations.

How to Know If The Fin Rot Treatment is Working?

To know if the fin rot treatment is working, you’ll see behavioural and physical changes in your betta fish.

If there were white fuzzy stuff on your betta, you’ll see it gone. You’ll see less inflammation on the fins and you can physically see the fins recovering.

Your betta fish will also stop being lethargic, regain its appetite, and begin behaving normally.

Once recovered, you can keep your betta in the quarantine tank for a little bit longer (a week or two) just for peace of mind before adding it back to the main aquarium.

However, it will take time for its fins to regrow. Continue adding tannins to your tank to encourage regrowth.

Preventing Betta Fish Fin Rot

Here are some helpful measures you can take to keep your betta fish safe against fin rot:

  • Keep your fish tank’s water clean by changing it weekly
  • Test your aquarium’s chemistry and parameters regularly
  • Vacuum your gravel monthly / deep vacuum every quarter
  • Use water conditioners meant for bettas
  • Avoid overfeeding
  • Try to get a large aquarium if you have too many fish
  • Regularly check for the early signs of fin rot
  • Monitor behavioural changes in your betta fish


In spite of the fact that betta fish fin rot can be unsettling for you and your pet, there are several treatments, both natural and medical, you can use to treat it.

When treated properly or early enough, your bettas will recover and do just fine. It’s uncommon to hear of betta fish dying due to fin rot, so don’t worry too much and follow the mentioned treatments.

Once fin rot is treated, most betta fins start to grow back into normal condition.

However, always adopt preventive measures to prevent fin rot in the first place.

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