With proper care and treatment, Betta fish usually grow back their fins in 4 weeks. This is true especially in cases of tail rot, where the fins will fray and shorten. If left unchecked, however, tail rot may deteriorate to body rot, which is more serious and can cause the bones of the Betta fish to become exposed and even lead to death.
Also known as fin rot, tail rot occurs when the water quality in the aquarium is poor. Apart from the obvious signs of shortening and fraying on the fins of the fish, Bettas may exhibit other symptoms, such as loss of appetite, and their color may darken.
Keeping the water clean prevents the onset of tail rot. In case regular aquarium water maintenance was neglected, the water must be changed completely once the symptoms in the fish are noticed. Adding ampicillin can also help speed up the recovery of Betta fish, and their fins should start to grow back within a few weeks.
Once tail rot progresses to body rot, the condition will be harder to treat. However, Betta fish afflicted with the condition can still thrive with proper and immediate treatment. To treat body rot, the water must be completely changed, and then changed regularly from that point on. Higher doses of ampicillin should be used together with BettaZing medication to help the Betta fish recover.