Astrea SnailHow to Care for Astrea Snail written by Dave Burr Astrea Snails are very effective at controlling the growth of undesirable algae in aquariums. They are a good choice to combat cyanobacteria and diatom algae. Astrea Snails can even help to control nussiance hair algae. They will scavenge the rocks and aquarium glass. Feeding: If no algae is present in the aquarium you may supplement the Astrea Snails diet with live macro algae or dried seaweed (nori).