From the start of this thread I came to the early conclusion that I had not been doing the slam the right way. Hence the reason algae spots would return after a couple weeks. Pool has always been clear and balanced properly. Just goes to show how persistent algae is. So I started the slam again the proper way. Took almost three weeks and cleaned everything, so I thought. I believe this could but have been shorter slam and less frustrating had I not skimmed out on the cleaning of the filter. As soon a I did a more detailed clean I had an immediate improvement in my ONLT.