Fin rot describes any condition that causes several specific symptoms. Like its name implies, fin rot is when a fish’s fin becomes infected or begins to rot away. If your betta’s fin has rotted away, the fish may have a severe case of fin rot. Fortunately, fin rot is treatable and preventable.
Fish with fin rot may appear to have small holes or rips in their fins. The edges of the fins might appear frayed or slimy in areas where the fin is actively rotting. Fish fins may be edged in white, which is a sign of infection. Parts of the fish’s fins may fall off. If left untreated, the fins may disintegrate all together, and the rot may start to attack the body of the fish.
Fin rot is most often caused by keeping a fish in dirty water. Fish that are stressed are also susceptible to fin rot. Fin rot may also occur in fish that have been injured by parasites or other fish. Open sores may become infected and invite fin rot. Temperature fluctuations in the aquarium water or poor nutrition can also lead to fin rot. Fin rot occurs in these situations because the fish’s health is compromised, and the fish itself is weakened. The fish’s immune system cannot fend off the bacteria that causes fin rot when it is already unhealthy.
Isolate the fish with fin rot. Keep the sick fish’s water very clean by changing part of the water frequently. Maintain a steady water temperature of between 72 and 82 degrees. Add one teaspoon of aquarium salt per gallon of water in the aquarium when treating slight cases of fin rot. For severe fin rot cases, add a fish antibiotic designed to treat fin rot to the aquarium. Continue treating the fish and keeping it isolated until the fins appear to be regrowing.
Keep the water in the aquarium clean and perform frequent partial water changes. Install a more powerful water filtration system in the aquarium if necessary. Don’t allow the water temperature to drop below 72 degrees or above 82 degrees. Feed the fish a balanced diet, and make sure that each fish in the aquarium is getting enough to eat. Keep peaceful fish away from fish that nip.
Other Causes of a Missing Fin
Because bettas usually live in small habitats and are susceptible to stress and water conditions, they commonly develop fin rot. However, fin rot does not remove a fin in an extremely short period of time, such as overnight. Although fin rot could rot away an entire fin, if your betta's entire fin has disappeared since the last time you looked at it, fin rot may not be to blame.
Consider the possibility that another fish could have nipped the fin off. If you feel this is the case, you can treat the injured fish in a manner similar to fin rot treatment. Isolate the fish, maintain water temperature and cleanliness, and use an antibiotic until the fin grows back. If you feel another fish bit the fin, keep this fish away from your betta in the future.