Help! Self Mutilating Betta!

[Amber]

I've had my fish for around 6 months with no problems until...A few nights ago I approached my male betta's tank to find he had his fin in his mouth! I think he probably caught it while slightly bent and when he straightened out it tore all the way up the middle and made two fins. He chomped away at the section in his mouth, and eventually spit it out (I don't know the name of this fin, it's the one that hangs from his belly). A few days later I found that one half of the fin was completely gone with about a centimeter of it left on his body, and the other half was split in two. He hasn't tried anymore self-cannibalism in the past week or so, but he looks horrible! Why'd he do it? Is he in pain? Can I help him? Will he look like this forever or will any of it heal or grow back? I feed him well, he loves his 3-5 daily little pellets and sometimes he gets kind of fat so I know I'm not starving him. What's his problem?

[CrazieEddie]

It will heal if you provide clean water and medicate it. If it's the only fish in the tank, perform at least a 50% water change the next few days. It's safe to perform large water changes for Bettas, but for most other fish, no more than about 30%.

It may have a case of Fin/Tail rot due to bacteria (normally caused by poor water conditions) and may be irritated from it. After the water changes, treat the fish with BettaFix or something similar to treat Fin/Tail rot for bettas. Also apply aquarium salt. Once the fins/tail looks like they healed, treat the fish with Bettamax for a few weeks.

Make sure you perform frequent water changes. Don't overfeed the fish, because this will lead to high ammonia & nitrITE levels, which leads to poor water conditions and bacteria.