Malaysian trumpet snails are hard to control as they give birth to live snails.
Personally i like them as they aerate the soil but when there is too many i put a piece of zucchini in the tank overnight, by the morning I can't see the zucchini for snails and just scoop it out with a net.
Added bonus is a little treat for the shrimp.
When you squash them try to aim for the larger ones to try and slow the breeding cycle.
Cheers mick