I have just read all the post about your problem and I have been dealing with the exact same thing for the past 3 weeks. All my test numbers look great except when I come home I have a powder of stuff on the bottom of my pool and on the steps and when we brush, it disappears in the water. I have treated it all along like algae. The water is clearer but the stuff still at the bottom. I left a post earlier called "I think it might be algae" and alot of helpful information, but every evening when I get home, the same stuff.