the best snail IMO is The Cerith snail it is a small scavenger with an elongated spiral shell that is usually black with tiny white dots covering the entire shell. One of the most ideal scavengers, detritus eaters, and algae eaters these snails are perfect for the reef aquarium, quickly devouring detritus, uneaten food, decaying organics, fish waste, and several types of nuisance algae. Cerith Snails will often bury themselves in the sand, which will help maintain adequate oxygen levels in the substrate.