Such a pretty boy, love him!
It does look like tail biting- which I would rather deal with rot because at least that way you can get rid of it, as opposed to tail biting which is a pain.
Keep up on your weekly water changes to avoid rot- keep an eye on the edges, if you see them go black, crusty, flaking off, or white cottony like growths on the edges, then it means he has gotten rot- which is easily treatable. Rot will form when they damage their fins (either from biting or tearing from another source) and the water is unclean. So routine water changes is a must with tail biters.
Heavy fins which you could baffle the filter and hope that will help cause less drag to allow them to build up their muscles and eventually allow them to grow out their tail once more (since prior to you buying them, they tend to never be in anything bigger then a half gallon- breeder jars are rarely a gallon size that the males are kept in prior to being cupped and shipped to stores). If there is no filter, and are large finned type, then there isn't much you can do in the way of stopping them. Hopefully he will grow a little stronger being in a larger tank and they won't drag him down as much.
Stress sometimes a great stress will get them biting their tails, sort of like a nervous habit- our version of chewing our nails when we get stressed. Sometimes when you buy a betta online and is shipped, the shipping process (being in a very small bag, not even really any room to turn) will cause them to start fin biting while being shipped so a lot of people will open their boxes to some sadly torn up fins.
Sometimes being in too open of a tank without a lot of plants or a place to hide will cause them to be stressed.
Even something as simple as moving them to a new home will cause it.
One of my boys started right after I went into surgery, and I couldn't be at my desk for a few weeks. He had never bit his own tail, but the whole time I was gone, he did.. (He is right here at my desk, and he's always getting attention- then one day I disappeared. Whether it's coincidence or he just missed me, I don't know. He has 2 neighbors, so unsure exactly his cause.)
Boredom If there isn't enough in their tank, or if they are alone most of the day then they could end up eating their tails just to do something. Bettas are actually social creatures, they love to interact with us, and having to be able to see other bettas can actually boost their spirit. (But not all, some are just strictly solo)
Aggression Some males get overly excited when flaring, and they want to fight- since they can't get at the mirror or other male, they will attack their own fins out of frustration. But a good flaring a day is a good thing!
He looks like the heavy fin type.. halfmoons are notorious for biting off their own fins. Hope he stops that, because would love to see his fins open fully and healthy, he is such a pretty boy! (can't say that enough lol)
Last edited by Myates; 11-11-2011 at 08:26 PM.