I just started a new SLAM because I suspected Algae.
Relevant stats are:
Pre SLAM PH: 7.4
CYA: a bit less than 40
I got too busy working on renovation stuff and just got to testing my water at 1:20 AM (I had added one more FC on a hunch at 9:00PM which got me right on the money for 16 at this test).
Sunrise is officially at 5:33 AM here, but the pool is west of the house, so it is a bit in the shade at first. If I measure FC at 6:30 or 7:00, is that long enough that less than 1 FC loss is significant enough, or is that too short? Right around the solstice and in upstate New York there isn't a lot of night to do this test.
I read a couple of other threads I found searching for OCLT threads but I didn't find anything that said less than 1FC in x sunless hours is the good spot. Also worth noting: No bathers today, but lots of dead bugs, leaves, and general tree junk in the pool. Other relevant details if anyone wants to know: I used my brush head vacuum on the whole pool after I got the shock levels up earlier in the afternoon, so everything was stirred and sucked into the filter. I also added some more DE. Oddly, after a while my filter pressure dropped (It went from 14 to 15 after I added DE, then went up to 17, and after a few hours back to 15). And after I connected my vacuum and turned on the pump my return spewed out a cloud of dark stuff, no idea what that was about.
Thanks for the help.