I have a 24,000 gallon in-ground pool/spa in Northern California.
My latest test results are:
FC normally run between 1 and 5 ppm (I add 1 gal 10% liquid chlorine when I get down to 1-2 ppm)
CYA 160 (diluted my water sample by 50% with tap water and ended up with 80 on the CYA test)
Why don't I have more problems with algae? My water is always clear and I can always clearly see the main drain 7 feet down in the deep end. I do end up with a slight green on the walls, but it easily brushes off (in fact the brush causes the green to literally fly away from the walls), and I try to do this once per week, although I have been known to go 2 weeks or longer between brushing. I do end up with white dust accumulating on the steps and bottom of the pool, and I assume this is bleached out algae.
Why am I not seeing green or cloudy water?
I realize that I am running FC at levels far lower than I should given the very high CYA level that I have. And I have considered going higher on my FC, but I haven't since my water looks so good. I have been on BBB for roughly a year, but have only used bleach and muriatic acid so far.
P.S. I end up using 2 gallons or so of 10% chlorine per week in the summer and as little as a gallon or two of chlorine per month in the winter.