Marine crabs play an important part in maintaining a saltwater aquarium. The two most important uses for crabs are the removal of algae and detritus. There are many different kinds of crabs and some are better than others in the removal of detritus and nuisance algae. Some crabs are just cool looking while others like the arrow crab are know to eat bristle worms.
Bubble algae eaters!
Fascinating and fun creature