I have had a recurring black algae problem for a number of years which I have never been able to successfully defeat. Recently I began following this site and bought my TF-100 which has been very helpful. In reading the SLAM and Black Algae posts, I felt ready to tackle the project. I adjusted the Ph to 7.2 and brought the CYA up to 70 with a goal of 75, but overshot and CYA is now 100. FC is 23 and will not seem to go higher. I am scrubbing the entire pool twice daily for the last 5 days and have seen some progress but it has been slow. Question: Do I need to drain water to get CYA level down to 75 for a salt pool? I have ordered the salt test kit as I suspect the salt generator is not working properly. In treating the Black Algae in the past I have positioned tri-chlor pucks over the heaviest infestation. It appears now that the plaster has been displaced, and the bare concrete is showing through. Can these areas be patched with the white plaster or must the entire pool be resurfaced?