First off, I want to say this is a great site and full of great info. This is our second year with the pool, last year I was winging it and after initial issues with no CYA in the pool/ chlorine depletion, things were fine. I just opened the pool this past Saturday, and water/pool was very clean/clear. I wised up and purchased the TF-100 test kit. Great kit. Pool truck topped me off on Monday evening. Ran equipment 16 hours after. Initial test results Tuesday evening around 5pm were as follows: PH 7.4, CYA 40, Chlorine 0. So, I applied a hair over 4 of the 128oz 12.5% jugs from late last year that I stored indoors. Continued running the pump and retested at 10:30 pm. Tested FC to be at 25, I believe my SLAM target would have been 16 FC. Did not get a chance to test early next morning like I should have, but tested at 5pm Wednesday as follows: PH 7.7 which rose probably from the high FC, FC 21, CC 0, Alkalinity tests high per literature I read. Tested again this evening same time around 5pm and FC 16ish, CC 0, PH 7.7 still a bit high. FC now at original SLAM target after 3 days with no CC and very clear water....am I wrong to assume I do not need to 'shock' the pool again? I only lost 4 FC after the first test/ 19 hours. Thanks in advance.