How Do Bettas Get Fin Rot?

3 min read

Bettas have become one of the most popular aquarium fishes because of their beautiful appearance. Because bettas seem to be easy to take care of (some people just leave them in a bowl), however if you don’t take good care of your betta, you will find yourself googling, how do bettas get fin rot?


Bettas get fin rot from bacterial infections eating away at their fins. Their fins are usually burned from dirty water or torn from fighting or scraping against something. The burn or tear in their fin sets the stage for the infection to set in. Fin rot can also be caused by too much stress which weakens your betta’s immune system.

Dirty Water

The number one usual cause for fin rot in betta fish is from dirty water. If you have a filter in your betta tank then you only need to change about forty percent of the water every 2 – 3 weeks.

If you don’t have a filter in your betta tank then you will have to change half the water every week if it is a small bowl and 30 percent of the water if it is a larger bowl.

The water changes are to keep ammonia from fish poop, harmful nitrites, or bad bacteria from building up. Every aquarium has ‘beneficial bacteria’ in it which keeps ammonia levels down.

However, since your fish are always pooping, even the ‘good’ nitrates can get at too high of a level in your tank. When you do a water change you are also supposed to vacuum the bottom of your tank with a siphon tube designed for this purpose.

When you take a certain amount of water out, you take out water with bacteria. You should vacuum the bottom of your tank first so when you take the bad water out you take any loose stuff that the vacuum jerked up.

You never want to change all of your water because you want some of your beneficial bacteria to remain.

Why Dirty Water Causes Fin Rot in Bettas

If you don’t change your water enough then the ammonia from too much fish poop causes too much bad bacteria.

This bacteria causes something like a burn that damages the fins on your betta. After the fin is damaged the bacteria eats away at the fins and can completely destroy them.

Why Fin Injuries Can Lead to Fin Rot in Your Betta

Since bettas are known as fighting fish, they can get into some pretty fierce battles if they have a tank mate. Sometimes their fins can get torn from fighting or they may even scrape their fin on a filter or tank decoration.

Its pretty rare for a betta to get fin rot from an injury if they are well taken care of. However, if the water is too dirty and your betta fish tears its fin, it may get infected by bacteria. Again if you keep your water clean, this is not likely.

Fin Rot from Stress

Your betta fish can also get fin rot from too much stress. This can happen from having too many tank mates which weakens their immune system. They could also get an infection this way from tearing one of their fins.


If you know your fish has fin rot because their fins are falling apart then it is easy to isolate them in a separate tank and treat them with over the counter or mail order medications.

The best way to avoid fin rot is prevention by changing their water, making sure they live alone or have good tankmates, and keeping them in a low-stress environment.

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Pet Aquariums

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