Personally, I wouldnt worry about them. Although they may be unwanted visitors, I dont think they are worth putting chemicals in the tank for.
I was as mad as Hell when I found snails in my tank, and tried all the suggested remedies - lettuce leaves, cucumber etc, but found the best way is just to either lift them out and chuck them out, or squash them against the side of the tank and feed them to the fish.
They dont bother me now, and in fact I havent seen a snail for the past couple of days so perhaps at long last I have got rid of them.
TROPICAL TANK-Elite Tank - 207litres
6 Harlequin Rasboras, 5 Emerald Eye Rasboras, 10 Cherry Barbs, 2 Bristlenose Plecs, 2 Panda Corys. 4 Dwarf Chain Loaches.
ViaAqua Tank AR620 97litres
1 red male betta, 1 BN