- red, black, BROWN, OR OTHER DARK outline around the edges of fins


- fins ARE GETTING shorter and shorter

- fins are falling off



Fin rot can be the outcome of either a bacterial or fungal infection. The most common cause for fin rot is stress due to dirty water conditions. Other stressors that cause fin rot include low water temperatures, and excessively moving the fish to new environments. This is why many pet store bettas have fin rot in their tiny cups that rarely get cleaned. If your fish gets fin rot then it is a sign to do more water changes and upgrade to a bigger sized tank. Fin rot is another reason bettas need at least 1 gallon of water to prevent harmful bacteria to build up. If you always keep your water clean then fin rot should never be a problem.



Move the fish to a hospital tank and clean out the infected aquarium and all of the items that were inside. Keeping the water clean is the most important factor to remember in treating fin rot. Keep the water on the cooler side of what bettas need, around 76-78F/24-26C to prevent the bacteria from growing faster.


For fin rot that you have caught early, a strong antibiotic may not be necessary. Many people swear by aquarium salt, sodium chloride, which is easily accessible and very cheap at fish stores. To treat with aquarium salt, dose 1 teaspoon per gallon for 10 days. You NEED to make sure you have freshly changed water before adding more salt, to keep the water clean and because salt does not evaporate. If you do not change to new water and just keep adding salt, your fish will die from too much salt in the water.


For fin rot that has gotten a bit too far, use a bacterial/fungal medication and follow its instructions. It may take up to a month to cure the fin rot so don't give up. Many people recommend Maracyn Two by Mardel and Fungus Clear by Jungle. My holy grail medication for almost all illnesses is Lifeguard by Tetra which claims to cure fin rot. However, I have not had to cure fin rot in years so I have no experience in curing it with this medication.