Staining

[pjlowepa]

I have never had this problem before and it appeared only this year. All along the bottom sides and bottom along the sides there is a strip of what looks like algae but will not come off with scrubbing. We have had this pool for over 10 years and the vinyl liner is 3 years old. We use stream water to fill the pool. The water is crystal clear. It is the worst on the side where the pool gets the most sun. I have used a great deal on algaecide with no results. I have read that it may be from metals in the water, but the water is clear and it only recently happened.