Healthy crowntail male Betta splendens.
Q: N wrote,
I think I have a tail biter. His caudal fin is shredded and there is nothing in the tank that could be doing it to him. No sharp plants or other fish. I have dealt with fin rot before with another betta and it doesn’t appear to be that either. Ammonia is 0, nitrite is 0 and nitrate is 12 ppm.
A: Well, it’s not totally unheard of for Bettas to bite their own tails. I personally haven’t dealt with it but I hear about it from others. I suspect that in most cases the ragged fins are a result of poor water quality or injury from tank decor or other fish. Too often people believe their betta is biting his own fins when the problem is environmental but in your case, I think you might be right. Based on the water parameters you provided, your tank is fully cycled and in good shape, at least as far as ammonia, nitrite and nitrate are concerned. If there are no sharp rocks, plastic plants or heavy filter suction to catch his fins then it’s possible he is doing it to himself. I recommend observing him closely to see if you can catch him in the act.
The reason Betta’s bite their own fins is unknown. Some say it’s stress, others say boredom and still others think it could be hunger, pent up aggression or even hereditary. The truth is, we just don’t know. There are a few things you can do to help him along. First, continue to keep your water very clean to avoid infection. Some Betta keepers have successfully broken the habit by changing the aquarium decor around or by adding more silk or live plants. Adjusting the light levels may be useful too reduce reflections which may fuel your Bettas aggression. If your aquarium is large enough, you may find adding a few peaceful community fish will keep your Betta occupied.
In addition to clean water, you can also add Pimafix or half strength Melafix to the tank to help regenerate fin growth. If your betta reacts to the medication negatively, discontinue use.