Wanted alls opinion on this thought. VHO Actinic Light running (10-12 hours day) passed six months can change spectrum which feeds hair algae. My tank has a bad out break and can not find why, talking to my LFS he had the same problem. Both our lights were 8 months old when the problem was at it worst. He changed his lights and added SAT every Monday and his problem is almost gone. I just changed my lights and add first dosage of SAT. Reason for this thought, is I have read a lot on this forum where people could not find the cause of there Hair Algae out break. Will update if the problem goes away with this simple fix. I never had hair algae before until my VHO were 8 months old. I have only had my new light set up for 8 months.