Doing a deep clean of the DE filter and found this in the pipes, and was also all over the skimmer basket. Decently easy to scrub off with medium pressure. In the middle of my SLAM and close to the OCLT, but have been stuck at 1.5ppm to 2.5ppm loose every night still. DE filter was the last thing to clean and it looked bad. But saw this in the pipes and don’t know what it is.