I am getting rather worried. I had another cory die and I am starting to suspect Rusty as nothing is wrong with the water or temperature and there was no sign of anything resembling a disease at all. The previous time a portion of one cory's caudal fin went missing. I tried medicating for finrot but in fact the little creature simply up and died. However more recently a cory with no symptoms at all other than severe anxiety died. I'd previously seen Rusty charging at him in particular during feeding time, and I've noticed him actually getting more aggressive with the corys, to the point of actually biting at them. Today he definitely bit one of the smaller ones. What should I do? Could it in fact be that my betta is slowly killing off the corys? I know it's not supposd to happen but I remember that way back when when I was a kid I had a tiger barb that did the same thing, slowly harassed other fish to death.