The media I am using in the calcium reactor is from a local fish store, it is not name brand. I had an algae problem before the calcium reactor and it has not worsened so I do not think its a contributing factor. The media looks just like the large ARM media. I always had low nutrients, 0 nitrate detectable and very low to undetectable phosphate yet I have always had small patches of HA. It doesn't get crazy out of control and most people don't notice it but it does p*** me off. I am religious with changing the media and filters in my RO system and feel I am doing everything by the book. I even have a litermeter for a continuous water change. I thought that the pellets would get rid of the HA but it doesn't seem to be doing much of anything. They run perfect no clumping mild tumble etc etc. I am thinking of removing the pellets and trying GFO since your not supposed to use the two at once. I blame the HA from not curing the dry rock I purchased from BRS when I first started the system. Ugh if I could start over I would definitely do things different.