Hey, I chose not to vote, because, although I'm not against euthanasia I don't really think that the fact that the fish kills is a good enough reason. After all, you could have given the fish away or kept it in a separate tank.
I suppose that if the fish was just mean, and would kill any fish it was put with, then it's kind of acceptable, but on the other hand I'm sure that you could always find a more aggressive fish that would keep it under control.
I don't really seem to have added much with this message!