For a better part of the summer I have had a mystery stain in a 4x6 area of the pool. the stain is faint, blotchy, green to tan in color and climbs the corners up onto the wall. I'd have said that it hasn't spread or changed at all, but i am now noticing a small similar stain in another, deeper area of the pool. The stain does not appear to brush off at all, and the initial area doesn't seam to grow or change.
During the summer, my water has been clear, and ,in general, has been maintained in recommended specs. There was a period, however this past spring where things got out of control.
I have shocked several times and have seen no change in the area. currently, I am shocking again, and brushing the area daily. Does anyone have any suggestions or recommendations as to what this is or how I can treat it? I have tried to take photos, but no matter what angle I use, they don't really come out well.
pH7.5 (FYI it CHRONICALLY rises to 8.2)
TA 60 (store says 100)
CYA 25 (store says 60)
CH 450 per the store (I can't ever seem to get a color change in my test kit)