The tennis ball looks as clean as when I dropped it in there...
So black algae? The paper towel was not green.

They take time to suck up the oily film floating on the surface. Like days worth of time. They are more of a preventative helper (going forward) and not a today cure. The existing oils are sticking to the skimmers and then attracting whatever dust/dirt/floaties are also floating around. Kinda like how an armor-all’d dashboard stays clean for all of 5 seconds because the dust that would have blown off then sticks to the dashboard. But boy is it shiny for those 5 seconds. lol.The tennis ball looks as clean as when I dropped it in there...So black algae
Yes.without reading the whole thread again - are you seeing unusual chlorine demand?
The outside of the skimmer won’t ‘trap’ the oils nearly as bad for them to accumulate. Neither will the stairs or border line. It will still be there too but not nearly as concentrated.Also just so you know, the outside of the skimmer doesn't have the line and neither of the deep end white steps have the line
That looks a little thicker than mine but you have had a lot of construction around the pool so that may be dirt and dust along with the grease. I have an auto cover and mine still gets the black accumulation even with little use. That just doesn’t look like black algae to me but I will defer to the experts.This... ?View attachment 358674
This makes me feel better.. thank you!That looks a little thicker than mine but you have had a lot of construction around the pool so that may be dirt and dust along with the grease. I have an auto cover and mine still gets the black accumulation even with little use. That just doesn’t look like black algae to me but I will defer to the experts.