I need some help figuring out what I've got going on in my pool. When we opened it 2 wks ago, it was dark brown. Actually, I think the water was fairly clear but the pool was covered with dark brown algae so it appeared brown. We've cleared it up but there is something on the bottom and sides of the pool that I'm not sure of. From a distance it appears to be a stain - a light, sand color, but if I look straight down at the side, I can see that it is not smooth. When I touch it, it feels rough, like sandpaper. It doesn't come off with the brush or vacuum, but if I rub it hard with my hand, I can rub it off. I'm wondering if this is some strange kind of algae or if it could be disintegration of my (old) vinyl liner.

I also have some residual dirt-looking stuff on the bottom of the pool in a few spots that does not clear up even though I've maintained shock level for days and the rest of the pool is clear. When I brush it, it clouds up and dissipates in the water, but settles out again by morning.

Any ideas or suggestions? Thanks!