snails will obviously need a source of food in order to live. be extra careful about wasted food that sinks to the bottom or decrease amount of food fed at a single time. depending on snail size and amount, you can probably hand remove the majority of them.
Put a piece of blanched lettuce in there over night. In the morning, remove the snail-infested piece of lettuce.
all very good ideas. i like snails and think they are great for tanks.hand remove the ones you can see and go through the gravel with a gravel vaccum to get rid of any eggs that could be in the gravel