Not sure what's going on. For about 8 or so hours yesterday, I got my CC to 0 and held on pretty-well to my FC levels around 22. It was overcast most of the day.

Suddenly, mid-day my FC dropped (by 8 ppms - twice) and my CC went back up (to 1.5). FC held at 25 overnight - but so didn't CC at 1.5.

I also did a polyquat treatment yesterday evening. The only other thing I did before the change, was brush part of the pool.

Question is - FC and CC are holding strong. Should I up the shock level?