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FIN ROT 🐠 Fish Disease Prevention and Treatment

Updated: Apr 19, 2021

About Fin Rot

Fin rot is one of the most common diseases we encounter in the fish keeping hobby, and it is especially common in bettas and goldfish. It is a bacterial infection that starts out attacking the fins of the fish, and it is important to catch this disease in its early stages, as more advanced stages of fin rot, can be difficult for fish to recover from.


The main symptoms of fin rot are the fraying of the edges of the tail or fins, the fin edges may have turned white, or black, inflammation at the base of the fin, and part of the tail or fin may appear to have rotten away. Other symptoms may include a loss of appetite, lethargy, or you fish sitting on the bottom of the tank.


There are a few different types of bacteria that are responsible for this disease, some gram positive and most gram negative, and it can be spread from infected fish to healthy fish, so when bringing new fish home, it is always recommended to quarantine them before adding them to a community tank.

In our aquariums, poor water quality, overcrowding, fish injuries, and stress can be major causes for infection.


The easiest way to prevent fin rot is by maintaining good water quality.

Keeping up with routine water testing and maintenance is a must to make sure that water parameters are where they need to be for the species of fish you are keeping. Always do your research, as species water parameter requirements can vary dramatically.

Making sure your tank is not overcrowded is also very important for prevention, as keeping a tank overstocked can quickly cause your aquarium to have poor water quality, and with too many fish in the aquarium, fish may start to show aggression towards one another, and could become overly stressed. Even in a properly stocked aquarium, if you notice aggression between fish, they may need to be separated, to prevent injuries and stress.

And lastly, take care not to overfeed your fish, as overfeeding can also quickly lead to poor water quality.


Treatment for this disease can be a lengthy process, and depending on how far along the disease is, it may require antibiotics. And as a quick disclaimer, some species of fish cannot tolerate certain treatments, this is often especially true for scaleless fish, so always research the species of fish you are keeping, before you begin treatment.

If caught early enough, doing large water changes of 40 to 50% and adding aquarium salt can often be an effective treatment. The typical dosage for aquarium salt is 1 tablespoon per 5 gallons.

In mild cases, some will recommend also using products such as Melafix or Bettafix to help aid in the healing of the fins.

For severe cases, a broad-spectrum antibiotic may be needed. Products like API Fin and Body Cure which contains Doxycycline, and API E.M. Erythromycin, containing Erythromycin, are often easy to find in most pet stores, at least in the U. S. For those outside the U.S. a prescription from a veterinarian may be required.

The most important part in treating fin rot is always maintaining good water quality, so you may need to do more frequent water testing and maintenance, to be sure you are giving your fish the best chance for recovery.

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