It depends. I keep my snails because they help keep the aquarium free of algae and I have carnivore critters who love eating them. They can overtake your tank, though. You can pick them and remove them by hand, or place a piece of organic lettuce (to avoid introducing pesticides into the tank) and watch them come over to eat it, then remove the leaf with all snails attached to it. You'll find their eggs everywhere, they are prolific breeders.