I have just discovered a snail in my terranium. I think it must have come from the pet shop as an egg on some plants that I bought recently. Can anyone tell me if it is likely to do any harm or if it can live quite happily in the tank with my Chinese FBNs? As far as I can see there is only one at the moment but thats not to say that there will not be more. Any help will be appreciated as I know nothing about snails.