You need rams horn snails rather than the bigger whelk shaped ones. they don't eat leaves.

Have you any turtles in your pond?

thats strange,most pond snails eat algea and not lilly pads,are you sure its the snails ?

Snails have rasping mouthparts which would create elongated holes in the leaves similar to what you see when a slug feasts on a hosta leaf. What I see here are leaves which are bitten off either by nipping fish or a turtle or two.

i knew it cause that lily pad would of still been ok and not looking so bad. thnx loosestrife