Hello, when I opened my pool this year I had black spots only above the water line. I've ran all my numbers when I opened the pool and slammed. Water looks amazing, but I cannot scrub the black dots off. I've used a hydrochloric acid based cleaner and it only slightly lightened them. I will post pics tomorrow. Any advice on how to scrub these off without draining my pool? Water is perfect like I said. Thank you for your time.
