Ok, here's where we stand. Current FC is 16.5 -- Target FC is 16.
Recap of the day (Overcast all day long, not a spot of sunlight):
6 am -- FC 7.5, overnight loss of 2 ppm, added 3 gallons of 10% as calculated by PM.
8:30 -- FC 21, whoops! Maybe pool size is off?
10:30 -- FC 19.5
1:30 -- FC 14, added 80 oz of 10%, using smaller pool size calc.
2:25 -- FC 20, whoops again!
4:00 -- FC 18
6:40 pm -- FC 16.5, pressure on the DE filter was up a bit, so I just backwashed for 30 secs and then recharged the filter with 6 lbs of DE. So it seems that it's definitely killing something in there.
So what should I do tonight? Add a bit of bleach, retest an hour later and then do another OCLT? Skip the OCLT tonight and shoot for doing it again tomorrow night? Let it go overnight at 16.5, knowing that it's probably/might be going to be under SLAM target by morning?
About to pour a giant glass of wine... cheers! And thank you!