If you don't want to get a snail eating fish you could put a small slice of courgette in tank overnight, and by morning it will be crawling with snails, then just pick them out. This method won't remove them totally but can be used to control their numbers.
Also, A local club member (Hawkes Bay Aquarium Soc.) had a method involving a piece of copper wire, for more info on this email/pm Zev she will have it amongst her minutes.
Hope this helps ...