We got a severe algae bloom when our sand filter control valve went out and it took two weeks to get repairs done and water flow back to the pool. We have made progress in this week using your algae treatment procedure. But with all the sweeping, backwashing, cleaning baskets and filters, and high FC levels using bleach; there is some stubborn black stuff on the pool bottom that is hard to sweep up.
Do you have any ideas that would make getting these black spots up easier?
Even though I couldn't pump and circulate water, would have sweeping the pool while waiting for service have helped to prevent this?