For the past two years I have been battling hair algae and excess nutrients in my 200 gal SPS dominated display tank. After fighting off acro-eating flatworms and then montipora eating nudibranches, I was never able to regain control of hair algae and my nutrient level. Even though nitrate (<5 ppm) and phosphate testing (<0.1 ppm) showed low levels of nutrients, rampant hair algae and poor SPS growth indicated that I had excess nutrients. I feed 1/2 sheet of nori and 2 cubes of mysis per day. I do 10-15% water changes every one-two weeks.
I tried zeoreactors with carbon dosing and bacterial supplements for a year and then tried 2 liters of bio-pellets plus bacterial supplements for a year, but conditions didn't improve. I had to try something else, so I set up an algae scrubber using the guidance of algaescrubber.net.
I am very, very happy with the results. I have been at it for 3 months now and results continue to improve. Hair algae growth is significantly reduced and gradually receding. More importantly, my SPS growth has returned to former levels, colors are better and polyp extension is better. Colonies that had shown no growth for many months are now sprouting new tips everywhere and visible growth of SPS colonies is quite apparent. Areas damaged by hair algae or cyano encroachment are repairing. All cyano has disappeared. Maintenance is very simple, clean the mesh once every two weeks, and I don't have to dose anything. I took the bio-pellets out two weeks after starting the scrubber.
My scrubber is 24" long and uses 2 10x10" mesh pads. Since my overflow return is too low to supply the scrubber, I pump 600 gpm water out of the sump into the scrubber supply tube which flows down the mesh and exits the bottom of the scrubber back to the sump. I have 4 x 2-17w 24" fluorescent fixtures with warm white bulbs that are clamped onto the outside of a clear acrylic box that the mesh pads hang in. The lights are on 18 hrs per day.
This is the growth I get at the end of two weeks, on both sides of each mesh pad. In total, I scrape off about 4-6 cups of thick wet algae every two weeks.
All the information you need can be found at algaescrubber.net or on Reef Central.