Since I have gotten the pool cleared up and looking good with the TFP method, I have been testing everyday to find out how much chlorine the pool needs every day. Eventually, I want to add an automated chlorine system to the pool. I tested last night after dark and found the FC to be 7.5. In order to get to my target FC of 9, the pool calculator said to add 67 oz of 10%. For the first time, I actually measured down to the oz instead of eyeballing it. When I tested this AM before the sun hit the pool, the FC was up to 11.5. Any ideas why this would happen? I messed with the # of gallons on the pool calculator and there would have to be a huge difference in gallons to make a big difference to the amount of FC change from 67 oz of chlorine.