I opened an older 1970's inground pool that had been abandoned for about 10 years. Concrete bottom, fiberglass sides. It had no chemicals added or anything done for 10 years, just natural rainwater (and we get quite a bit here in Ohio). Fast forward, rented a trash pump to get rid of large amounts of debris. Pool is in a rural area with fields and trees around it, so there was quite a bit of muck. Added the CYA, etc, and used large doses of chlorine.
Water is now sparkling, and the concrete bottom is clean and unstained. However, the fiberglass sides are stained brown, and very stubborn. Brushing didn't even phase it, and test areas with a scotch-brite pad had minimal effect.
I know about Jack's stain ID kit, but the water has to be at least 65-70 for accurate ID tests. This pool won't be there for months, if at all. It is poorly located between two buildings which block sun too much of the day, and no heater.
So, how to get rid of the stains on the fiberglass? Do I super-duper mega turbo chlorinate it?