Ya know I was wondering the same thing. I did put in 3 hermits and a Nassarius snail in it. I would advise against putting snails. Luckily I was checking my Skimmer often to adjust cause i found the snail stuck in the intake. Must not have been there for long because it was alive. The hermits have been in there for about 3 months and still alive. I do throw a pellet of food in there once a week.