Ive had my tank for about two years and have NEVER had a problem with hair algae. Its not a huge problem but i dont like the sight of it. Im not using an RO/DI yet so that could be a factor as i also have cyano growing on my sand bed. I siphon it out every two weeks when i do a water change. On the top of my tank i have a sunpod 150 Watt X 2 in the middle and on the back i have a PC fixture with 2 65 watt ultra actinics. It only seems to be growing on the rocks under the actinics. Also i looked in my overflow cuz i have a reef ready tank and its growing in the openings where the water flows into the overflow. Is this a problem?? I mean should i scarpe it off to get rid of it cuz maybe its restricting water flow into the overflow? Please help cuz i hate hair algae. I would like to get rid of it without getting a type of fish that eats it before it gets real bad. Also i do not have any sort of clean up crew. Only 2 red leg hermits that i got for free. Could high phosphates be causing this? I am going to test my phosphates at my LFS tomarrow to see what my levels are... Ok tested my levels and the phophates in my TAP water are 2.0ppm and the Phosphates in my tank are 0.5ppm