Scarlet reef hermit crabs, also known as red legged hermits or red reef hermits, are a beneficial part of any reef aquarium eco system and can grow to a maximum length of 1.5″. you will want one per every 3 gallons of water or 2 for every 3 gallons if lots of algae. They have brilliant red legs and claws, and a delicate yellow face with black and green eyes. Scarlet reef hermits are scavengers and will eat filamentous algae, diatoms, detritus, and occasionally cyanobacteria, making them a helpful part of the aquarium clean up crew. These hermit crabs are better suited for nano reef aquariums compared to other species as they are more peaceful, and less likely to attack or kill another hermit crab or snail for their shell. Scarlet reef hermits, like all hermit crabs, will occasionally need to change their shell in order to accommodate their larger size as they grow. They will also occasionally molt their exoskeleton, usually done at night when the aquarium lights are off. A new exoskeleton will harden after molting, and is aided by maintaining a proper iodine level.