I am new here. Never again to the pool supply store. Last night I used my test strip and the pH and all other readings were within an acceptable range. Two weeks ago I went to the pool supply store about the 3' x 1' black stain only in the deep end. They told me it was organic and to put in 'Leslie's Stain Remover' [ascorbic acid compound] followed an hour later by 'Natural Chemistry Metal Free'. It turned my water light green. I shocked it for two days and it was still green and we went on vacation for a week. Upon return I vacuumed and put in 'Aqua Chem Shock Xtra Blue, with algae fighting crystals' (63.05% Sodium dichlora-s- triazinetrione, 0.26% copper [metalic], 36.69% other ingredients) and it turned the water lime green. First, how do I get rid of the lime green? Second, once clear, how do I get rid of the black stain? Many thanks!