Assassin Snails, will eat other snails.
Snails are bad if they are overpopulated and cause problems with nitrate concentration.
Cucumber, lettuce, carrot or broccoli in a plastic bottle overnight should do the trick. Pull the bottle out in the morning, freeze and trash. Freezing will prevent live snails from possibly entering waterways.
To prevent overpopulation, feed less and gravel vac more.