I thought I read here at TFP that you lose half your FC every day? I supershocked my pool to 29 ppm on September 8th and am surpised it has already come down to about 6-7 ppm here on the 11th....I'm doing an overnight FC test to make sure I'm done shocking, but by the looks of the water, I would say so...I'm not sure I really had mustard algae, which is why I shocked to 29 (CYA 50)...I'm going to bring it up to 13ppm the night before I close...does this sound good? Thanks, all you awesome people, this has been a trouble free swim season!