Fin rot, also known as tail rot or fin erosion, is a common bacterial infection that affects the fins and tails of fish. It is one of the most prevalent fish diseases in both freshwater and marine aquariums. Fin rot is caused by various opportunistic bacteria, including Aeromonas, Pseudomonas, and others. The condition is typically a result of poor water quality, stress, or injuries, which weaken the fish’s immune system and make them susceptible to bacterial infections.

Symptoms: The symptoms of fin rot typically start with fraying or shredding of the fin edges. As the infection progresses, the fins may become shorter, and the rot can extend towards the fish’s body. In severe cases, the infection can reach the fish’s body, causing open sores and inflammation. Affected fish may exhibit signs of lethargy, loss of appetite, and changes in behavior.

Causes: Fin rot is often triggered by poor water conditions, such as high ammonia or nitrite levels, low oxygen levels, and excessive organic waste. Stressors, such as sudden changes in water parameters, overcrowding, aggressive tankmates, and inadequate nutrition, also contribute to the development of fin rot.

Transmission: The bacteria responsible for fin rot are commonly present in aquariums and natural aquatic environments. The infection can be transmitted through direct contact with contaminated water, infected fish, or contaminated equipment.

Treatment: Treatment for fin rot involves addressing the underlying causes and providing proper care for the affected fish.

The underlying bacteria responsible for fin rot are already profiled in Aeromonas and Pseudomonas infections.  Refer to that discussion for more detailed information and treatment.