Dave suggested I start a thread here in response to my post in this thread;
EWKearns - phosphates - Page 2
Here's the relevant part of what I posted;
"...I had a situation last season where I got some algae growth on one wall despite keeping FC at or above the recommended target level (never below 6ppm FC with CYA at 70-80ppm...more typically 6.5-7ppm FC; I use a SWCG), maintaining borate level at 50ppm, and passing all 3 SLAM criteria with flying colors (edit: before the algae appeared). I do have to use a sequestrant (Jack's Magic Purple Stuff) to prevent staining (despite metals testing negative using the "bucket test" method), hence my interest in the phosphate subject.
I am not a new user and have been following the methods taught here for many years. Last season (late August) is the first time I saw algae and has me puzzled. Btw, a SLAM took care of it and it did not return the rest of the season (closed early October). After that incident I didn't let FC drop below 10ppm for the rest of the season."
Could high phosphate level be to blame? I've not tested for phosphates since its been taught here that it's irrelevant when maintain proper FC levels. I assume my pool might have a high phosphate level given the steady diet of Jack's Maguc Purple Stuff.