i started with a just a few snails and thought "hey there cute, and there cleaners, what could go wrong?". well they've overrun my tank in little over 6 months. they spawn like mad and grow at an alarming rate as well. so asking around i came across these bad boys
there called "assassin snails". they will devour all snails in contact with water, and rather quickly at that. as far as i know, they are a freshwater creature, so without a water feature this will not work. you only need one, unless you want to clear out the snails very quickly for after they finish off the snails they will eat each other. also since snails use the water to breed they will keep more from spawning. even if it cant reach all the snails in your tank, it will at least have a good hold on population control.