Hi All, almost at the end of a SLAM - water is crystal clear, 0 CC and passed OCLT last night. I'm holding FC levels at 16-20 ppm for one more night. Before I started my SLAM over 3 weeks ago (I closed pool with green swampy mess last year and finally had time to watch it after summer vacations this year), my CYA was 0. I've added 8 lbs to my ~ 25,000 gal inground pool. CYA was added just before, and somewhat during the SLAM. CYA testing during SLAM was 30-40 ppm, but now I am showing 0. I'm confident my FC levels never dropped below 16 ppm, and I know 8 lbs of CYA was added to the water (sock dangling over return method, I'd give it a good squeeze over once/twice a day). I just changed my DE filter grids, but it was a good 2 weeks after the CYA was dosed into the water. The one thing I have changed is I ordered new taylor reagent. Could this possibly be it? Should I take water sample into pool store to check? Or just get more CYA going?