I had similar looking algae on my sand but it did not cover my corals. I still have some in areas now but not to bad. My phosphate and nitrate had bottomed out. Tank was cloudy to. Glass dirty everyday. I removed my chemical media except for a bag of carbon in the sump and my skimmer. I dosed neonitro and neophos to get both those numbers up. Corals came alive, tank is crystal clear and now I clean the glass once a week. Not perfect yet but much better.ill be sure to monitor everything super close while dosing! If its just a simple case of nitrates ill be stoked!