What can I do to get rid of this cyano. I had lights blue for 2 weeks and saw a huge improvement. Went back to white and BOOM came back speckled on the sand. There's phosguard in my filter. But still, all this algae, macro and the turf. They are reading zero but algae is still growing like crazy even under blue. When I test phosphates, it's undetectable with a Red Sea kit. Nitrate (between 0 and 5 ppm) and nitrite (0ppm) pH (8.2) API kits. Just want to avoid chemiclean and other chemicals. Please, recommendations.