Stains are on the walls of pool where the water line was while it was closed. I rubbed a vitamin c tab on it and it disappeared.
I saw the pool school article on how to do an absorbic acid treatment but I was wondering it an entire absorbic acid treatment is needed since the stains are new this season. Is there something I can just add to the water to make these disappear? Also is a sequestrant needed? I never added one in the past.
I have a 21000g SWG pool/spa with plaster. All chemical levels are within range as done with my TFP-100 kit.