What Causes Fin Rot In Bettas (Symptoms & Treatment Guide)

Betta Fin Rot Symptoms And Treatments

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You love your betta fish, and you want to keep it healthy for as long as possible. Unfortunately, betta fish fin rot is a very common problem that can make your pet feel uncomfortable and sad. You may not even notice the symptoms at first, but treating fin rot quickly is the best way to avoid severe fin rot developing.

Betta Fin Rot is typically caused by a bacterial infection, brought on by poor water quality or a lot of stress, but the result is always the same: decaying fins and tissue that leads to your betta fish losing its beautiful colors. White milky fin edges are a good indication of betta fish fin rot.

Betta Fin rot (also known as fin melt), is a very common condition in betta fish and can be caused by several reasons, so it is important to understand how to treat betta fin rot before it gets too serious.

This article will talk about the causes of betta fish fin rot, how to spot the symptoms of fin rot in betta fish, and how you should treat the condition if it does show up!

If you are new to betta fish, I also have an article called Setting Up A Betta Tank (The Right Way!), which is well worth a read.

Also, make sure to check out our Betta Fish Care Guide And Species Overview.

What Does Fin Rot Look Like On A Betta

If your betta fish has fin rot, it is very easy to miss the condition unless you know what you are looking for. The most obvious signs of betta fin rot are:

  • The fin tips become pale, milky white, transparent, or yellowish instead of their usual vibrant colors.
  • Parts of the fin rotting away and falling off (this can happen within a few days!).
  • The fins become stringy or frayed with jagged fin edges.
  • You may also notice that your betta fish has a mucus-like film on its body, indicating fin rot.

When the infection is fungal, the fin edges will be less stringy and frayed and instead will rot more evenly and become more white and fluffy.

When suffering from severe fin rot, betta fish have quite a hard time and will probably stop eating and sleeping which will make them grumpy. A male betta’s fins are large and flowing, so when fin rot sets in, the fragile membrane can become heavily affected, often ending up with a large amount of fin loss.

Any fin loss will eventually grow back, however, the quicker you can spot the onset of your betta fish fin rot symptoms, the quicker you can treat it. If caught really quickly, your betta may only have minor fin loss around the edges.

The video below will give you many examples of what betta fin rot looks like.

Betta Tail Rot Signs, Symptoms and Treatments

If you don’t treat your betta fish right away when it has fin rot, this condition will worsen. The decaying tissue starts to spread all across the fins and infect other areas of your betta fish’s body.

There are many different treatments available to treat fin rot in bettas. I will discuss some of these treatments a little later on.

What Causes Fin Rot In Bettas

Betta fin rot is a common bacterial disease. It will also be called tail rot, gill rot, mouth rot, or body rot, dependent on where the bacteria is found.

There are many ways betta fish can contract this condition, but it’s important to understand the most common causes, so you know how to prevent them!

The main cause of betta fish fin rot is poor water quality. If your tank isn’t properly maintained and all levels (ammonia, nitrate, and nitrite) aren’t checked every week, your betta fish will be more susceptible to bacterial infections.

Bacterial fin rot can be caused by many bacterias classed as gram-negative such as Aeromonas, Pseudomonas fluorescens, or Vibrio, which eat the soft, delicate membranes around the fins.

A Fungal infection will often develop at the infection site, appear white and fluffy, and can be referred to as fungal fin rot. Fungal fin rot is most easily noticed when your betta fish fins are turning white at the edges.

If you have a sick betta fish, fin rot can set in much quicker because the immune system is already compromised. There are many parasites and bacteria often present in a betta tank just waiting to strike when a bettas immunity is down, and this is the best time for fin rot is most likely to happen.


Another more serious bacteria that can evade the most common treatments of fin rot is Mycobacteriosis. If the treatments you have tried do not seem to clear the infection, your fish will probably have this type of bacteria.

Illustration of aquarium bacteria close up
Illustration of aquarium bacteria close up.

If any of these bacterial infections are left untreated, the fish will usually die.

Several causes can lead to bacterial fin rot, such as:

  • Stress causes a betta’s immune system to be down. A lowered immune system can also be caused by other less obvious problems.
  • Poor water quality.
  • Injuries from fighting and fin nipping other fish or other betta fish in the aquarium.
  • Parasites (eustrongyloides) can cause fungal infection (fungal fin rot).
  • Keeping the aquarium heater at the wrong temperature.

Is Betta Fin Rot Contagious

Because fin rot on betta fish is caused by certain bacteria, it is contagious if the bacteria is allowed to spread. Whether betta fin rot is contagious or not, the environment is already saturated with the harmful bacteria that cause it. Keeping fish apart will not stop the fin rot from spreading to other fish, instead, you will need to treat the entire tank.

Although fin rot is contagious, your betta will still need a lowered immunity for the bacteria to take hold and cause any damage. As I mentioned previously, the harmful bacteria which cause fin rot on betta fish are common, and often go unnoticed with no ill effects.

Betta Fin Rot Symptoms

Apart from looking at your betta’s fins, there are several other symptoms you can look out for like:

  • Lethargy
  • Loss of appetite
  • White or light gray patches on the fins and body. These patches are usually found on the edges where they meet other fin rays but can be any color (not just white).
  • Rubbing the body up against objects in the tank, or even other fish to try and get relief.
  • Finding your betta hanging at the top of his aquarium without being able to swim downwards. This is because he feels like he has no energy left to move around!

If you notice any of the above symptoms and if they are due to fin rot, you will probably notice some of the more obvious physical signs of betta fin rot.

Some of the symptoms above are also common in diseases like white spot, better known as ich/ick.

If you haven’t treated the betta fin rot early enough, these rotting patches will eventually start to spread across other parts of the body.

Betta Fin Rot VS Fin Loss

It is sometimes hard to distinguish between betta fin rot vs fin loss from other tank mates nipping at your fish’s fins.

As betta fish are quite aggressive toward other fish, they often meet their match and become the prey. A betta’s fins are delicate and attract a lot of attention from other fish.

In my early years of fishkeeping, I tried betta fish in my community tank. The betta seemed a little timid, and I guessed it was because of the new environment, but after a good night of sleep, I looked In my tank and couldn’t see my betta anymore.

After 20 minutes of looking, I noticed this strange creature wobbling around the tank with no fins. IT WAS MY BETTA!! which soon died.

Not understanding why this had happened, I tried one more betta and discovered that both my Angelfish and my Gouramis were systematically fin nipping my betta until all of its gorgeous plumage was gone.

This is a drastic case of fin nipping, and it will often happen on a much smaller scale. As betta fish have such long wavy fins, they are an easy target for most fish to nip at, and this will cause many recurring infections.

The damage caused by fin nipping will often progress to fin rot as the damaged fins are more susceptible to bacteria and parasitic infection.

Fin Rot Or Nipping

It is usually quite easy to distinguish between fin rot or nipping.

The most common signs of nipping are:

  • The fin edges around the missing area will appear clean-cut as opposed to being tattered and frayed, which would indicate damage from other fish.
  • Ripped fins or split fins may be caused by fighting, and although may not be nipped, the damage can be caused by sharp objects in the tank.
  • If you have recently added a new fish to the aquarium, then it is highly likely that they are responsible for nipping at your betta’s fins.
  • A timid betta that is hiding out in the fish tank.
Fin Nipping In Betta Fish
Fin Nipping And Fighting In Betta Fish Is Very Common.

As already mentioned, damage caused by nipping can be the trigger for betta fin rot to set in, so it is important to quickly move the perpetrator to a separate tank or a separate container if you only have 1 tank.

If a betta fish fins rot, it is quite easy to distinguish from nipping because they are so colorful and delicate, the mushy dark appearance will usually stand out quite well.

Betta Mouth Rot

Mouth rot in betta is a bacterial infection and is also referred to as mouth fungus, cottonmouth, or cotton wool disease because it appears like mold or a white wooly fungus. Betta mouth rot is caused by Flexibacter Columnaris or Flavobacterium Columnare bacteria.

Early Stage Betta Mouth Rot

In the early stages, your betta’s mouth rot may cause a loss of appetite due to the discomfort caused inside their mouth. At this stage, you may notice some small strings of a white, cotton-like substance protruding from your betta’s mouth.

As the mouth rot progresses, you will certainly notice a white substance coming out of your betta’s mouth and the mouth rot can spread to the gills where it will affect breathing.

Treatment for betta mouth rot will be the same as for fin rot which I will describe in more detail below, but as it is a bacterial infection, a simple over-the-counter anti-bacterial medicine should be quite effective in most cases.

During a case of mouth rot, it would be worth changing your betta’s diet to something more manageable other than pellets. The best food for betta fish will be something soft and easy to eat. Your betta won’t want to chase live food around the tank when they have mouth rot, so frozen or freeze-dried food like baby brine shrimp, or bloodworms may help.

How To Treat Fin Rot Betta

One key factor in how to treat betta fin rot successfully is to recognize it in the early stages. Betta fin rot can be caught at many stages, and you will often be treating fin rot differently at each stage. Early-stage fin rot will cause less initial damage and be easier to treat.

Always check water parameters and water temperature first.

Treating Mild Fin Rot On Betta Fish

Mild fin rot is when caught at its earliest stage. Only the fin edges are usually affected and may look a little soft and melted.

Mild fin rot treatment is usually more simple. Just add aquarium salt to the aquarium water. You can buy aquarium salts at most pet shops, and you just need to follow the guidelines on the label.

Medication may or may not be necessary. If you don’t feel the infection is clearing or don’t want to take the chance of it spreading, use one of the medications listed below for moderate fin rot.

If you are in the stages of mild fin rot, you should definitely check the water quality in your aquarium and ensure the proper temperature is set and maintained.

Poor water quality is a main contributing factor of fin rot and can be caused by uneaten food debris, poor filtration, and a general lack of cleaning.

All of these factors will eventually lead to a build-up of the bad bacteria, which can cause fin rot.

It is important to carry out regular water changes and use a gravel vacuum to remove any debris from the substrate. Regular water changes will keep bacteria levels down, and the result should be healthy fish.

Treating Moderate Fin Rot In Betta Fish

Moderate fin rot will need immediate attention, especially if your betta has an aggressive personality.

If you have caught the fin rot at this stage and immediately move the infected fish to a quarantine tank, it will be easier for treatment.

As already mentioned above, aquarium salt can help heal mild or moderate betta fin rot, but it is not always easy to ensure all of the water in your fish tank is covered with aquarium salt.

By using betta fin rot medication, you can treat any type of betta fin rot easily and effectively without adding salt.

Three medications that are effective against betta fin rot are:

BettaFix For Fin Rot by Aquarium Pharmaceuticals

API Bettafix For Fin Rot

MelaFix For Fin Rot (Malachite Green) 16 Fluid Ounce Bottle

API Melafix For Fin Rot

Fritz Aquatics Mardel – Maracyn 2 Antibiotic Treatment

Mardel - Maracyn 2 Antibiotic Treatment For Fin Rot

These medications can cure mild to moderate betta fin rot in only one day, however, you need to change 50% of your fish tank water before adding this product, and it can be harmful to any live plants or invertebrates.

These medications are highly recommended as they will act fast and need minimal changes to your tank conditions.

There are many more medicines available, and you should always check whether they are treating bacterial, fungal, or parasitic infections (or all 3).

Moderate betta fin rot treatment can also involve adding aquarium salt daily until the infection clears up. This will not cure the infection, but it will reduce your betta’s stress levels, reducing fin rot.

API Aquarium Salt

API Aquarium Salt

Treating Severe Fin Rot In Betta Fish

Fin rot treatment is easier if caught early. Severe fin rot treatment is more time-consuming, will take longer to act, and is often far less effective. Advanced fin rot can cause a fast decline in the health of your betta fish, and it may die.

Ideally, move your betta to a quarantine tank as soon as possible. The quarantine tank will stop other fish from contracting fin rot so easily.

Change your aquarium water every day and add betta fin rot medication twice daily for up to five days.

You should notice a difference after only one day of treatment. Still, you must complete the full dosage until all signs of infection have gone away completely before stopping the medication.

The use of betta fin rot medicine means you don’t need to change your aquarium water so drastically.

If the betta is still eating, it will tolerate a small amount of medication in its tank. If your betta stops eating, this would be a problem and potentially be a sign that your betta is dying.

In this case, remove all medications from the tank immediately and do a 50-60% water change to lower the medication levels.

It is important not to over-medicate your betta and always follow the manufacturer’s dosage advice exactly.

Although betta fin rot treatment should be easy, you need to ensure that any medications used will not harm other fish or plants in your aquarium, as this could lead to secondary infections, which are harder to treat.

Can Fin Rot Heal On Its Own

It is possible that fin rot can heal on its own. A betta will usually become more susceptible to the infection if the immune system is down. Should the betta’s immune system improve, it may fight the infection without medication.

Personally, I wouldn’t rely on this happening and would always want to treat an infection as early as possible as bacteria and parasites can spread quickly through the aquarium water.

If you have a community tank, other fish risk contracting fin rot.

How Long Does Fin Rot Take To Heal

How long does fin rot take to heal is difficult to answer? The infection itself can be treated and cleared relatively quickly, although the physical scars need to heal.

Betta fish will experience fin regrowth over time (usually several months), and the fish’s body will heal quite quickly. Providing there is no major fin damage, you will need to wait patiently and nurse your betta fish back to health.

How To Tell If Fin Rot Is Getting Better

You can tell if fin rot is getting better by your betta fish’s general mood, and the fins should appear less mushy.

It does take time to notice any real physical signs, as there needs to be some fin regrowth first, so it is easier sometimes to make sure the condition is not getting any worse.

As long as the fin damage has stopped, you can be assured that the fin rot has been cured.

As fins begin to grow back they will have a transparent appearance and they will be very fragile at this stage of re-growth.

Betta Fish Fin Re-Growth
Betta Fish Fin Re-Growth Can Be Seen As A fragile Transparent Edge.

How To Prevent Betta Fin Rot

The best way to treat betta fish fin rot is through prevention, so let’s find out how to prevent betta fin rot and ensure you take all the necessary steps.

To prevent fin rot, it is advisable not to overcrowd your aquarium and keep the water clean at all times, checking water parameters regularly. I have a great post on How Often To Change Betta Water – What you need to know.

This will also reduce stress levels in your betta fish which could cause their immune system to be compromised as they fight off infections or parasites.

Also, you need to ensure you are not overfeeding your betta. Feed only what they can eat in two minutes and remove any uneaten food after this time as it will pollute the water and increase nitrate levels which could lead to fin rot developing.

Betta fish living in a clean tank with plenty of space will boost their immune system. They will not feel overcrowded and will be much less likely to contract fin rot.

The steps to prevent betta fin rot are pretty simple, but too many fish owners will ignore the basics and end up having to treat fin rot instead, with potentially devastating consequences.

Wrap Up

Betta fin rot is a preventable disease that’s caused by too much stress on the fish. If your betta has an open sore or wound, it will be prone to infection and could get worse if not treated right away.

If you notice any of these symptoms in your pet, make sure to take them to the vet for treatment as soon as possible. It’s best to avoid this problem altogether with simple steps like keeping your tank clean, so bacteria doesn’t grow there and being mindful about how you feed them food – they’ll be less stressed when eating well!

Frequently Asked Questions


Wikipedia – Fin Rot

University Of Florida -Use Of Antibiotics In Fish

The Aquarium Wiki – Fin Rot

Jon O'Connell

I have kept both marine and freshwater fish and set up almost 100 aquariums. Happy to share my knowledge and experience to help others enjoy keeping healthy and happy fish.

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