Thanks PoolDoc! I have the mesh cover on - doing as you said. When I tested 0 CYA, took a sample to Leslies - they showed 45 CYA - took another sample to another store - they showed 25 (lol) I ordered new reagent and retested - it's 0. Leslies also tests phosphates - they showed 0 (for what its worth). Only lost 2 ppm chlorine overnight - I put 1 bottle Clorox in this morning and its holding so far at 15 ppm. I'll try the phosphate stuff if you think I should. Oh, meant to ask, should I put my Polaris in while shocking? I've scrubbed it and soaked in Clorox. Thank you!