For the duration of this new SLAM I am definitely back to 24 hour a day pump operation. The stuff poofs up when approached softly with the brush. I understand that usually points to algae? If algae, I don't know if it is dead or still alive--it looked yellowish, much like what I fought off during my SLAM weeks ago. I don't have the influx of tiny flowers or floating pollen on the surface this time though-- last time I was dealing with both at once.
Thinking through what might have happened, I'm wondering if the water level starting to drop from a new pool water leak, combined with use of an attached intex skimmer might have contributed to poor water circulation at the opposite end of the pool from the return due to the pump maybe not being strong enough. But then again, the stuff on the floor was arranged in closely spaced lines so that suggests water circulation being adequate there?
I have removed the skimmer attachment and the flow limiter on the other intake port to have the pump filter flow rate as high as possible, and I have rinsed off the cartridge. I do not have have a pressure gauge on this pump so I rinse it off weekly during normal times, and check daily during SLAM.
(Removed reply to duraleigh, seems I answered the pollen question here before I read it)