You did not tell us your Free Chlorine or Combined Chloramine levels. You may well have an algae bloom. Either that or some sort of metals in your water. Try putting some Ascorbic Acid (Vitamin C) on the stain and see if it fades it. If it does, it is metal and our metal removal experts can advise you.
In my opinion, your approach will not work because it is not getting at either problem, algae or metals, and you should leave your pH and Alkalinity alone.
Bookmarks