Stain is approx 1/4 around pool. Have had it for 2 yrs. This year it is getting darker. Have tried liq chlorine on rag, magic eraser, plain cotton rag. Get very little off. Tried vit C in sock and did nothing. Water is clear and balanced. Thoughts?
Not sticky. Not raised. All above waterline.Is it sticky? Is it raised? Is it all above the waterline?