Never, but never, acquire a fish or another snail to deal with this issue. Other fish have their own needs to be healthy, and may have more problems associated with them than benefits if they do eat snails. If the tank is suited to such fish, fine, but most of us with this issue do not have this. Similarly, never use chemicals (no one has suggested this in this thread, but it has been advised in others). These are always detrimental to fish, and perhaps beyond.
Colin's method is the only safe one. You must ensure the snails do not somehow get into the local ecosystem, as by being inadvertently flushed down the toilet (thinking they are dead when they are not, hence the crushing). Assassin snails are not the answer; there are now areas in the USA where these somehow got into the environment and have decimated the natural snail populations.