Towards the end of the summer I was measuring a CYA of 20-25(yes my kit goes that low but it is on the bottom end of the measurement so I'm not sure how accurate that was but adding stabilizer by the calculator I was close because I targeted 30 and didn't miss it). My water temps during max usage were getting into the 90's and the pool gets sun all day long in the hot and humid south. I quit working with the how many ppm Fc target in the afternoon thing "after" adding chemicals and went to trying to achieve a residual "before" adding chlorine at dark that was on target of 3 or 4, with 4 being my goal. This seemed to work well and no algae or icky water all summer. Some days I could do well and then other times when the bather load was varied it was a little harder. It seems to me some people are "ickier" than others . The shorter days and cooler water temps really make a big difference when combined with no swimmer loads. Some days in the summer I was adding 2 gals of 6% to get the residual I was looking for and that was with a solid reading of 25 on my cya. Later in the summer I let cya drift below 25 probably close to or below 20 and still had basically the same chlorine demand day to day. Thanks for the responses!!!!