Yes, backwashing is standard maintenance. The Deep Cleaning should be done maybe once a year, unless you have problems. Since this system is new to you, you would have no idea what might be happening inside the filter - or what previous owners might have had added.Well I did backwash which I will have to do again. And at this point, I might be on the verge of draining a lot to lower that CYA count.
Btw, I only see part 1, and I can't view part 2! :-(
Viewing part 2 works for me. Folks, ideas?
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That's interesting and makes it less likely to be yellow/mustard algae. You might get a skimmer sock to put over the skimmer and see if you collect anything that looks similar. If you do, then that's falling into the pool (could be pollen) and some is sinking to the floor and not getting circulated or caught in the filter. That would also be consistent with the fact that the SLAM didn't kill it.
Richard, I may be missing it, but I don't think OP did SLAM the pool. In the beginning when OP mentioned starting the SLAM, he thought his CYA was about 35, but has since confirmed 85 ish.