In another post, I see that someone recommended a total blackout. So, figured I had nothing to lose. I taped dark green towels around my tank, but left the top open just by the filter for air flow. It's been two days, and I did peak today, and it still looks just as green. I think the phospates were fine when it was tested last week, but my next step is to get the "phosphate absorbing medium" previously recommended. Unless there are any more ideas out there.