We have a 15 gallon tank, that we tried to establish with a school of five tiger barbs. Within a few weeks, they were down to two, with the others having been picked to death by a bully fish. We introduced four more. The bully fish killed them too, plus his original tank mate. He's now been alone for almost a year, and is completely healthy. Candidly, we've been hoping he'll just die, so that we can start again with a different breed of fish. My wife has even talked about euthanizing him, and I've been tempted given his past capital crimes. But before I do that, I was wondering whether re-homing a single brutal fish is realistic. I was also wondering if there were other species of fish we might introduce into the tank that will co-exist even with an angry tiger barb. I can't return him to the fish store, as he came from Petco and they won't take live returns.