The fact is that almost all plant nurseries have snails living on their plants. It's their natural habitat and that's the way it is. Some snails can be bad for plants, others can be beneficial in a planted tank. Ramshorn snails, for example are bad and Pond as well as Apple snails are quite good to have in a planted tank. Malaysian Trumpet snails, on the other hand, make sure your substrate doesn't have dangerous gas pockets by constantly burrowing in it. In the beginning, I hated the idea of having snails in my planted tank. But as they're found in almost all plant nurseries, of course they hitched a ride to my tank when I ordered my plants online. I have Pond snails. To tell you the truth, while they do lay eggs here and there, I don't see that many of them in my tank and not one of them has grown bigger than a fingernail. I don't overfeed and this is probably what keeps the snail population under control. And they're kind of cute to watch cleaning algae. Yes, they do eat algae, just like algae eaters. This is comething you should read:
http://plantgeek.net/article_viewer.php?id=14. Another fact is that snails are rather hard to avoid in the planted tank hobby, so if you can't avoid them, accept them.
If, however, you're really intent on not having any snails whatsoever in your planted tank, there is a certain solution you can buy in which you bathe your plants before you put them inside your tank. It kills the snails/snail eggs on the plants. I don't know if it does any damage to plants, but my guess would be that since it kills snails, it may damage the plants in some way too. BUT, I may be wrong, since I never used this solution. Sorry but I don't know its name either. I think Carol knows it (not sure).