Hello, all! I've learned so much on this forum and website I'm beginning to feel like the master of my pool!! Just recently I have noticed a film that accumulates along the waterline at the tile. It only happens on a few tiles around the perimeter of the pool. It doesn't feel slimy, it kind of feels as if someone scribbled on the tile with a crayon. I just use my pool sponge to clean it off. Is this algae? Or is it residual sun screen, sweat, hair products, etc? I monitor my pool levels in accordance with the information provided on this website/forum and my water is always clean and sparkly. Thanks for any information!