Having a problem keeping algae away. I keep FC between 4-6 and CYA is 60-80. We have had some rain and haven't swam in 4-5 days and I keep it covered with a solar cover. When I take the cover off you can see algae in the corners and creases of the deep end and also some on the deep end floor. I know everyone says phosphate levels don't matter but I'm beginning to wonder? Thoughts? Thanks!