I totally feel your pain. I am experiencing the same thing. All my numbers are good; the water is clear, but this brown dusty stuff keeps showing up everyday on the bottom. I am told it is not algea or it would be on the sides and steps. I am sick of daily vacuuming but I don't know what else to do. Oddly, after I vacuum if I leave the filter off it stays clean. Only when I turn the pump back on does the dusty stuff come back. I'm thinking of trying a skimmer sock to see if I can catch this when I vacuum. Let me know if you have any ideas