What Does Fin Rot Look Like On A Betta Fish? [Vet Explains]

Does it look like there is something wrong with your betta fish’s fin? This could be fin rot. If your fish has fin rot, there are something that you need to do at home to help treat this and keep your betta fish from getting very sick and even dying. 

What Does Fin Rot Look Like On A Betta Fish?

The tips of your betta fish’s fins will look ragged and may be black to red in color. 

If your betta fish has ragged edges you will need to figure out why they have fin rot and change a few things to help treat their fin rot. 

What is Fin rot?

Fin rot is a gram-negative bacterium or a fungal infection that is seen in betta fish.  

This is very common in fish tanks that are small and not cleaned often.  This infection will attack your betta fish’s fins.  Most fish that you buy from large pet stores may already come with these issues due to them not being cleaned or living in very small cups until they are sold. 

What causes fin rot?

Usually, fin rot is caused by your fish becoming stressed due to poor tank conditions.

There is no need to stress this can easily be treated and most of the time fish will not die from this issue. These are some things that you need to check to make sure that your betta fish’s tank is at ideal conditions. 

Poor water quality

Your betta fish tank will need to be cleaned often. Your fish is eating, peeing, and pooping in their tank. If you do not clean this, it will get very gross very quickly. You can check the water parameters of your tank. These are a few parameters that you need to check:

  • Water temperature (Ideal temp: 75 to 80)
  • High ammonium level (>0 ppm)
  • High Nitrite levels (>0 ppm)
  • High nitrate levels (>20 ppm)
  • Incorrect pH levels (ideal 6.5 to 7.5)

Other causes of Fin Rot

While poor water quality is the most common reason for your fish to develop fin rot. These are some other things that can cause fin rot: 

  • Overcrowding and having too many fish in your tank can cause your fish to be stressed
  • Over feeding or under feeding your betta fish
  • Weakened immune system or other health issue

What are the signs and symptoms of Fin Rot in Betta Fish?

Depending on how severe your betta fish’s fin rot is and how quickly you catch fin rot will determine what signs you see. It is best to check your fish each day and if your notice anything wrong with your fish start to treat them for fin rot. The top, bottom, and tail fin are the most common fins that you will notice that your fish has fin rot. 

  • For a mild case of fin rot, you will notice brown, jagged fin edges with white spots on their fins.
  • For moderate amount of fin rot, you will see that the fins start to deteriorate and recede. These fins may be bloody and may start to develop fuzzy growths on the edge. 
  • For severe cases of fin rot, you will see redness and inflammation at the base of the fin. The while fin may be lost. This infection can even spread to your fish’s body. It can lead to your fish becoming lethargic, have issues swimming and maybe even develop other dieses. 

How to treat Fin rot in betta fish

There are many things that can be causing your fish to have fin rot. Once you figure out what is causing this it will be very easy to correct these issues. 

Change the water

If your fish tank has not been cleaned regularly it is time to clean your fish’s tank. A dirty tank can cause your fish to become stressed and lead to your fish developing these infections on their fins. 

Change the filter

If your filter is not clean or it has not been changed very recently it would be best to change or clean your filter. Your fish is eating peeing and pooping all in the same water they live in. If you do not keep their tank as clean as possible, they can get sick very quickly

Check the temperature of the tank

Betta fish like to live at a certain temperature. During the hot summer months, their tanks can get very hot and in the winter they can get cold. You should always make sure that your betta’s tank is kept at a constant temperature.

What Does Fin Rot Look Like On A Betta Fish? [Vet Explains]

Betta fish’s tank should be kept between 75 to 80 degrees. If your fish’s tank is too cold you can use a tank heater to help warm their tank. In the hot summer, you can use a chiller to help cool the tank. 

Give your fish Antibiotics

If your fish has an infection, you can give your fish antibiotics. If you have a large tank with a lot of fish, it would be best for you to set up a hospitalized tank for your fish to live in. 

Common antibiotics that you can use to treat fin rot are Maracyn II, API Fungus Cure, API Furan-2, Kanamycin. You can find these antibiotics at most big box pet stores or online. The directions for how to dose these medications to your fish are found on the package. 

See your Fish Vet

While most vets do not see fish but there are some that do have some fish knowledge. If your fish is very sick, try reaching out to your local vet or even a fish store to see what vet they recommend.

The fish store may also be able to give you some advice on things to do to help your fish feel much better.

How to prevent my fish from developing fin rot?

Sometimes fin rot cannot be prevented but making sure that your water parameters are at the correct ranges and cleaning your tank often will help decrease the chances of your fish from developing fin rot. 

Also, make sure that there are not too many fish in your betta fish’s tank. These extra fish lead to more waste in the tank and overcrowding leading to stress and more disease issues. 

What is the prognosis of fin rot?

Most fish will survive fin rot and their fin will eventually grow back. This condition is also not very contagious to other fish in the tank unless the other fish have a suppressed immune system.

The earlier that you detect that there is something wrong with your fish and start treating fin rot the quicker your fish can return to a normal happy life. 


Fin rot is commonly seen in betta fish that live in an unclean tank. Cleaning your tank very often and making sure that all of your water parameters are at ideal levels. Once you notice that your fish is having issues, it is best to start checking water parameters and start treatment if needed. 

If your fish is very sick, it would be best to try to find a fish savvy vet in your area or reach out to your local fish shop. While fin rot is not deadly it can suppress your fish’s immune system making the susceptible to other issues.