I started to salt my fresh water tank and haven't had a snail issue. After an outbreak, I ran all my decor through the dishwasher (no soap), scrubbed the sides of the tank to remove eggs (little yellowish blobs), rinsed the plants again, using my hands to rub off anything snail related, and followed the directions on fresh water salt adding. Blue cardboard milkbox type container.
The salt also aids the fish, treats and prevents stuff like Ick. You can give a salt bath if they have some sort of affliction, and then just follow the directions as part of the water treatment plan.