I had a severe algae problem in my tank...hair, green, and a bit of bubble starting. I had a yellow tang, who was trying to keep up, but is too small, so I got 3 medium everald crabs, a large algae blenny, and some cleaner shrimp. Don't know if the cleaner shrimp do anything to the algae, but wherever they hang out, within a day or two, there is no algae. Besides that, in about two weeks, my algae problem was GONE. Completely gone. I cant keep snails alive in my tank, so crabs and fish were the answer for me. And if the emeralds ever get to agressive, I'll use a crab trap to get them out. Just my .02