I'll second that motion! I too have the black ring in the skimmer (which I know is from all the suntan lotion getting into the pool), and even started to realize the tile area above the water line was getting hazy and covered over with "gunk". Based on both recommendations from this forum (THANKS!), I threw a scum ball into each skimmer and one into the pool itself (this one didn't do much help in the pool and wound up in the skimmer - that's fine), and am amazed at just how much that black line has now transferred to the scum balls; and then also used a Magic Eraser on the tiles and restored their shine instantly!! I simply swim around the pool with the Magic Eraser, wiping down the tiles and in about 10 minutes it's all gone!!
I understand there are various "enzyme" products on the market to help breakdown some of these oils and residue. I'd be interested to hear others opinions on any of these products. I haven't looked into them myself yet, so wasn't even sure if there is a particular one worth any while.