The Blue Leg Hermit Crab, (Clibanarius tricolor) is good at removing hair algae and detritus, and fair at removing some kinds of cyanobacteria and film algae from your tank. They will spend their time on the rocks and on the substrate of your aquarium, with a preference for the rocks.They are safe to add to most macroalgae planted tanks, but will consume some fleshy algae like scroll algae, halymenia, and ulva.