I had a huge hair algae outbreak for over a year. I tried all types of herbivores: rabbitfish, yellow tang, a gang of scarlet hermits, turbos, astreas, powder blue tang, and a sea hare - which didn't last too long. I think that herbivores can help control a minor outbreak, but not a large one. For me getting nutrients under control was the key. I always had an RO and figured that must be good enough, because the water always tested zero for nitrates and phosphates. When I bought a TDS meter I learned the RO was missing quite a lot. So I added a DI to the RO. After several twenty percent water changes and some manual siphoning of larger strands, the hair algae went away and hasn't been seen since. Some phosphate remover and rinsing frozen food before feeding can't hurt either. Other things that didn't work were taking out the rock and scrubbing it (looked great for a week or two) and changing out the old bulbs for new ones. As for a phophate kit I like the Salifert one. The DD kit or a colorimeter are better, but quite costly.