How do I remove this?

[nateb]

Looks like stains from leaves...gurss I couldn't depend on the kids swimming out while I was out of town.

 

[YippeeSkippy]

Try putting a chlorine puck on the stain and seeing if it lifts it? If that doesn't do it go get some cheap chewable Vit C tablets in a sock and bash it a bit to break them up in the sock. Then hold the sock on it a few minutes to see if that is the magic that lifts it.

Chlorine puck works= organic stain
Vitamin C works = metal stain

You haven't added any cheap algaecides that contain copper, have you?

Maddie

 

[jragan]

If it’s a mostly shaded area in a generally warmer climate then I’d guess it’s algae.