In my tank one loach and 5 ghost shrimp keep the snails at bay. I've never found snails in my tank, but tons of babies in my canister filter. I dumped them all into my tank. I watched the ghost shrimp eat several (cool to see), and I'm certain my loach eats it's share as well. that was 2 months ago. I still find them in my filter quite often, but I've never seen anymore in the tank. Any I put in the tank from the filter disapear with a day. You can see the broken shells, but never a live one.
Colin