Mark, you need to find the source before you can control it. Describe every detail of your system and what are your current parameters? How long have you been set up, do you have a sandbed, what kind of flow, what kind of water, skimmer, feedings, corals, cleaners, fish......everything man. I had a horendous battle with HA a good 6mths or so ago. Was phosphates, which imo is usually what the problem is.