I've read many threads of people trying various fish (Lawnmower's, Tangs.. etc) and nothing really seemed to work "Short-term" for them.
What seemed to work best, is finding what is fueling the growth of their hair algae, and removing that. Usually phosphates & nitrates. Additions of a Fuge, where other algaes are allowed to grow, seems to also help by having an ideal envoronment for those algaes to grow "external" to the main display system, so the nutrients required to fuel algae growth just aren't available in the display tank.