Betta Fish Fin Rot: Symptoms, Causes & Treatment

In our last article, we discussed at length about the causes and treatments of constipation in bettas. Today we’ll discuss another common yet dangerous disease in bettas which are fin rot.

I’m sure most of us have experienced neglecting our fish from time to time only to find out some ‘white fluff’ growing on your fish or even see parts of their fins fall off for unknown reasons. That’s fin rot.

Fin rot is caused by bacterial infections caused by the likes of Pseudomonas fluorescens, which causes ragged fins and fungal infections, which cause white fluff.

Generally, fin rot is caused by bad water quality resulting in a weakened immune system, causing the fish to be much more susceptible to a bacterial or fungal infection.

What is fin rot?

Before we dive deeper, let us take a step back and take a look at what fin rot is. Fin rot is usually characterized by the ‘disintegration’ of fins on the betta.

Some telltale signs can include but are not limited to :

  • Frayed fins
  • Torn fins
  • Inflammation or swelling around the base of the tail or fins
  • White fuzz growing around the fins
  • Discoloration
  • Parts of the fin falling off

Most of the time, these signs are usually accompanied by other behavioural oddities such as the lack of activity or the loss of appetite. However the signs can also come with a seemingly healthy and active fish.

Usually, if I see any of these signs in combination, I’d automatically assume that my fish has fin rot and make the necessary precautions.

Interestingly, this condition is usually caused either by bacterial or fungal infection and is relatively easy to remedy if spotted early. But if left untreated, it will quickly kill the fish.

Also, if not treated, fin rot tends to spread rather quickly in a community set up. Due to the bad water quality, other fishes in the same system will also have compromised immune systems and will quickly catch these infections.

Stages of Fin Rot

Fin rot usually comes in 3 stages, early, intermediate, and advanced. That said, these are terms that keepers have come up with that depict the severity of the fin rot.

Of course, there are also reasons as to why they are split up into the 3 stages. Because treatment in each stage is slightly different than the other. We’ll go through the treatments in the following sections, but for now, let me do my best to paint you a picture of each stage.

Early Stages Fin rot has the highest chances of survival when spotted at this stage. However, this is also the most difficult stage to spot. To make matters worse, sometimes the fish seems to be active and eating well.

It is characterized by minor discolorations, tears in the edges of the fins, and might show white spots.

Intermediate Stage At this stage, survival is still highly likely if cared for properly. Fishes that have reached this stage often show some lethargy, reluctance to eat, and have a relatively pale outlook.

The intermediate stage usually shows large proportions of the fin being absent with multiple ‘white fuzzy’ growths developing around the edges.

Advanced Stages In my experience, most of the fishes at this stage do not survive, however those that do generally recover with quite a bit of scarring. Fishes at this stage usually display very lethargic outlooks and seem to have a lot of difficulty swimming and maintaining balance.

This stage is characterized usually by chunks of fin missing, sometimes entire tails missing. Often, there is blood and swelling involved with “white fuzzy” growths all over the body.


Fin rot generally happens because of poor water quality which then leads to a compromised immune system in the fish.

Usually, fish such as bettas are more than capable of handling and warding off bacterial and fungal infections, however like any sick animal, once their immune system is compromised, their ability to fight off illness is degraded.

To add, there are other possible causes as well, such as overcrowding, overfeeding or feeding expired food, etc. All these are possible causes of stress which will also lead to fin rot.

Bettas are usually most at risk because of the way they are raised, in small tanks or jars, and can easily be neglected when you have hundreds or even thousands of fishes.


Fin rot is an easily preventable disease, especially in a fish like a betta, which is supposed to be a very hardy and disease-resistant species. Usually, when you spot fin rot on the betta, they’ve likely been living in stressful conditions for a long time before succumbing to the disease.

That said, prevention is incredibly easy. Here’s a simple method for you:

Water Keep up your maintenance schedule, remember to make your water changes.

Space Is the tank you’re keeping the betta in too small?

Stress Are there other sources of stress in the tank? like other tank mates, overcrowding?

Food Are you feeding a balanced diet? Are you overfeeding?

This is a method that I came up with when I was a novice that I still use today. It basically acts as a reminder to myself whenever I am caring for any fish, whether their needs are being met. When in doubt just remember WSSF!

Maintaining water quality is something every fish keeper should strive for. Not only will it save you a tonne in medication expenses, it will also ensure that your fish stay healthy for a long time to come.

But sometimes even the most experienced of keepers has a slip up here and there. That said, as long as you keep your water in a pristine condition, there’s really little to worry about.

Many novice keepers tend to struggle with this concept and rush to buy medication at the first sign of trouble.

So here’s another nugget of wisdom for you, “Take care of your water and it will take care of your fish.”


Like I mentioned earlier, different stages of fin rot require slightly different treatments. So for this section, I’ll split it up into the 3 stages of fin rot.

If you’re not sure what the differences of the stages are, refer to the section above.

Early The first thing to do is always do a large water change and remove the infected fish if it is in a community tank.

This large water change should be at least 50% of the tank’s total volume and should be done with de-chlorinated tap water.

De-chlorinated water is important because chlorine also adds another layer of stress to the fish and might kill the fish if the levels are high enough.

After the water change is done, make sure that the tank is in a clean pristine condition. Meaning you should ensure that the tank is free from anything that will cause a build-up of excess nutrients, i.e leftover food, poop, etc. Vacuum the substrate if any and be sure to clean the filter and all the decor.

Once the tank is clean monitor the water parameters, ensure that temperature is stable with no fluctuations. Make progressive water changes (25-30%) once every few days up until you see improvement in the fish’s condition. This can take a week or 2.

Intermediate At this stage, your fish still has a good chance of survival so be quick with your actions.

I would suggest making a 70-80% water change at this point in order to flush out as much of the bacteria or fungus in the water column.

On top of the water change, I would also add some dissolved Epsom salt into the tank. Generally, 2- 3 teaspoons (for a 5-gallon tank) of Epsom salt will do the trick. Epsom salt reduces stress and is said to enhance recovery in fish.

Mix the salt in a separate container before adding it into the tank. This step is crucial because adding undissolved salt to the tank can cause salt burns to the fish.

Once done, continue to monitor for improvements in the fish during the coming weeks. Generally, this can take up to a month for the infection to clear up and another few weeks for the wounds to heal.

Continue the water changes (20-30%) once every other day as this will greatly increase the chances of survival of the fish.

Advanced If your fish has already reached this stage, be prepared that it will likely not make it. At this stage, we will need to make some drastic moves in order to have the best chance of survival.

First, remove the fish from the tank and place it in another tank with fresh de-chlorinated water. Ensure that there is a bubbler or a sponge filter to increase aeration in the tank. This new tank will serve as the hospital for your betta. Clean out the old tank completely.

Prepare some form of medication. I personally recommend API Melafix as it has given me the greatest amount of success for sick fish. However any commercially available medication specifically for fin rot will work just as well. Follow the dosing instructions.

Once done, continue to observe your fish for the next few weeks as it will be crucial. Make water changes (20-30%) every other day.

If the fish survives, you will see signs of improvement usually after the first week.

Continue to keep the fish in the ‘hospital’ until it is completely healed before returning it to its original tank.

What can be done to improve the chances of survival?

I cannot stress enough how much you need to be consistent with your efforts when dealing with a sick fish. The chances of survival greatly increase when you work with consistency.

That said, I also have had success using blackwater as a treatment method for a few cases of severe fin rot.

Blackwater is essentially the same water the betta originates from and is said to reduce stress and soften the water, essentially boosting its immune system. It can be created by buying blackwater extract or placing some Indian almond leaves in the tank.

Keepers in Asia often use blackwater as a form of medication to treat ill fishes and boy do they swear by it.



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