Hiya David. Firstly, the snails wont hurt the fish at all although they can be a bit of a pain once you have them. There a couple of ways to get rid of them - or at least kerep the numbers down to an acceptable level.
You can put a piece of lettuce (weighted down) into the tank at lights out, and in the morning you will have snails on it. Just remove it, and the snails, and keep repeating till the snails are gone.
Another way is just to squash them against the side of the tank and feed them to the fish - they will love the extra treat!
There are chemicals you can buy to dose the tank with, but many people dont like to use them unless the problem becomes really severe. They can be dangerous to some fish by the way..
I have had snails in my tank for about 6 months now and use the squashing method every day to keep the numbers down a bit.
:lol: