Or you can buy a snail trap.
I use this for my planted tank.
Pros:
-No chemicals.
-Put in once every 2 weeks or so.
Cons:
-Fish/Shrimps can get trapped as well. I had this stupid cory that kept getting trapped inside. I let it out a total of 6 times. When I woke up in the morning, it was inside again.
I'm thinking of modifying it...Might try after exams.
-Can't get them all. This depends on you, I want some snails around to eat the algae and whatnots. So I don't mind this.