Scarlet Reef Hermit CrabHow to Care for Scarlet Reef Hermit Crab written by Dave Burr The Scarlet Reef Hermit Crab is a superb algae eater, and will even eat filamentous algae and cyanobacteria. It is very useful in keeping reef aquariums clean and free of undesirable algae. Growth: As the Scarlet Reef Hermit Crab grows they will need larger shells to take the place of the shell they outgrew. Place several old snail shells in the aquarium where the Scarlet Reef Hermit Crab