I have pond snails in all 3 of my tanks and I have noticed something, my 40 gallon with sand and cory cats has the least visible snails and I am not seeing new ones. What I do see is the cory cats will sit still and eat something out of the substrate I can't see. No flake food reaches the bottom and they will eat what they are finding rather than pellets sometimes. Are they eating young snails and snail eggs? I have read this possible, what else could they be finding in the sand?