Usually MTS won't over populate, they spawn as long as there is food to be eaten(Algae,food,decaying plant matter). SO they will usually top off at a certain balanced point where there is a perfect amount of snails to food ratio.
If they do become too populated you can always put them on top of some wood and smash them with a hammer, and then toss them into your compost pile or trash can.
Smashing them is necessary to give them a quick death over suffocating or drying out in the compost or trash can.