One of my fire-bellied toads started going blind a few days after I brought it home from the pet store. It got noticeably thinner than it's tank mate, who is a bully. I fed them each a superworm and the bully (a male) ate his and stole the worm out of the other frog's mouth. I now feed them separately, about a half-inch of water out of the big tank goes into a critter keeper and I put the male in there and let the other eat in peace.