The Red Leg Hermit Crab also known as Mexican Red Leg Hermits are common, tiny, powerhouses used extensively in the marine aquarium hobby for control of nuisance algae including hair algae, diatoms and cyanobacteria. Red Leg Hermits also serve to clean up any uneaten food and help keep the tank, rock and sand surfaces clean. Red Leg Hermits will generally grow slightly larger than their Blue Leg cousins. Size per individual is roughly 1/2” – 1” shell.