The way to control snails is really quite easy. You avoid excessive food and they don't reproduce as quickly. Then when you remove them, you can actually remove them faster than they reproduce. To remove large numbers at once, try placing a piece of a lettuce leaf in the tank at lights out and pull it out, snails and all, when you turn on the lights by surprise at night. The snails will often cover that lettuce piece.
tried for ages aswell
