Yeah, hermits are good at eating problem algea from rocks, but other than that they're trouble, imo. I'll probably get some of the new tank I put together but unlike the snails, if hermits die, I don't replace them. Down to 2 in my nano after starting with 5 over 6 months ago. I've definitely replaced all the snails that the hermits have killed, regardless of how many empty shells I've left strewn about. My determination is that when they molt, if they can't find a shell close enough to where they're hiding, they'll kill a snail that may be closer.