I would have thought there is a good chance they'll leave the snail, it is different from fish, but I must say I have no experience of keeping them with snails. Experience with fish, yes, and not very happy- they were little sweeties until one day.... IME it has nothing to do with being brought up with other fish and being used to them. Still, of course there may be exceptions. I personally wouldn't risk it again, but you can't be 100% sure what's going to happen.