Neil, don't be mad at the tetras. It must be assumed that something can go wrong. Everyone has different ammounts of sucess with tank mates, seeing as each fish will have different personalities. Your tetras might need more room, they might just think of him as another schoolmate (the pecking order in schools can be rather rough and full of nips). They are okay tank mates, but for the most part, the only tank mates that are "fool proof" in that they won't attack the betta (you'll never really know if the betta will attack them) would be snails, sometimes ghost shrimps, cories, and ottos. All of them are extremely shy, out of the way sort of tank mates. With more active tank mates that are as spunky as tetras it can never be assumed that they will never do something that might stress/hurt your betta.
Also, did you see them bit his tail? or are you just assuming?
Last edited by JKfish; 04-24-2011 at 05:41 PM.