I don't think copper is the best remedy. Copper is also toxic to inverts like ghost shrimp if you have any. The copper also can linger in the substrate for a long time and may, over time, harm the nervous system of the fish. I know "over time" is vague, but I wouldn't want to expose my fish to a chemical when I didn't have to.
If you have room in your tank, you could get a fish that would eat the snails. Only consider this option if you have room for the adult fish and want a fish like this in your tank. He will still be in your tank after the snails are gone, so make sure this is a good option for you.
An easy way to control the snails is by weighing down a piece of lettuce and putting it on the bottom of the tank at night. In the morning, snails will be clinging to the lettuce and you can just lift it out to remove the snails. This may not get rid of them completely, but it can control them if you do it often.
What kind of snails are they, do you know? Pond snails are "pests" in an aquarium. They are very small and look like little footballs. Malaysian trumpet snails have a spiral shape and while they can get out of hand in a small tank, they are usually considered beneficial to a planted tank.
