Emerald/Ruby Mithrax Crab
Mithrax crabs have dull claws that allow them to scrape algae from your liverock, and are good at removing bubble algae, hair algae, dictyota, some species of caulerpa, and other complex macroalgae. The size of your bubble algae problem will largely determine the amount of emerald crabs that your tank will need to get the job done. Mithrax crabs are omnivores, and will also scavenge for food. They prefer to spend their time on hard surfaces that they can cling to.