Fish rot is indicated by the erosion or shredding of the fish’s fin, normally beginning at the outer end. It can be bacterial or fungal, and can be caused by a variety of common reasons, such as poor water conditions, diet, or injury.

Once diagnosed, fin rot is generally easily and quickly treated, as the fish’s fins can be regenerated, unless the condition progresses past the base of the fin. This is extremely dangerous to the fish as, with bacterial infections, it can be absorbed into the body of the fish and subsequently kill the fish.

Fungal fin rot usually rots more evenly, and produces a white edge; while bacterial fin rot produces more of a jagged edge. In many cases, both can be present at the same time, creating the need to treat both kinds. In more advanced cases of each, there may be redness or inflammation.

The type of fin rot in your fish will determine the method of treatment you use. Fungal fin rot is easiest to treat, generally by swabbing the infected area with an antiseptic, such as malachite green, (also called aniline green and a number of other names).

Bacterial fin rot in fish is normally treated with a form of antibiotic in a quarantine tank. This can be stressful to your fish, however. I more preferred method is the use of food containing an antibiotic.

In advanced cases, the rotted area may be removed, but the fish will have to be sedated.

Fin rot is easy to diagnose and treat, and most times your fish will survive, if treated , properly. It is important to remember, though, that since fin rot is normally the result of some other stress to your fish or its environment, you must also address these issues in order to prevent it from reoccurring.