I have been having this problem the past couple of years. I get large brown patches and streaks throughout the bottom of my pool. It must be algae because if I super shock with 4 gal of liquid chlorine it disappears. As soon as the chlorine level comes down a little to maybe 10 it re-appears. It doesn't scrub off. It seems/looks like a stain but it can't be because heavy chlorine does the trick. Keeping the pool heavily chlorinated knocks off my ph. What is it ? How can I get rid of it permanently ?
My ph is 7, cya 80.