Here is the story. I had not one issue with it when I was running my two 175 MH 14k lights. I switched to my T5s with brand new Guissmen bulbs about 8 hours per day (14k, 10k, Pure Actinic, 14K) and about a month or so later hair algae started growing everywhere. I cut back to just two bulbs and it still grew.. also tried cutting hours back.. still grew. I have been using RO/Di water since the start, and all water changes are the same. Parameters are fine, but I bought some phosphate remover and ran that, and cut my light down to just this simple little led strip for about a month. Also did two 20% water changes and bought new DI and filters. SO.. it basically was gone about a week ago. Then I started running just two of my T5 lights again about 8 hours. Corals all started perking up nice....but as of two or three days ago the hair algae is starting to cover ALL liverock again! Please help. I just don't understand the problem. I'm very tempted to put the MH lights back on and see what happens.