FC = 5
pH = 7.4
TA = 70 (Just added baking soda to bring it up to 90)
CH = 250
CYA = 50
Had pool replastered on June 2007. 10/2007 - 4/2008, covered pool and didn't attend to it over that time. April of 2008, cleaned the pool and kept it clean, except for 1 or 2 algae blooms until 10/2008. 10/2008-6/2009 reduced water level below skimmer several inches, covered pool and didn't attend to it over that time. Finally got it clean after considerable work (Refer to http://www.troublefreepool.com/diary...mp-t15087.html). Since then I have kept it clean except for the occasional algae bloom which I dealt with quickly.
Because of my actions the pool walls were stained from a couple inches below the skimmer down. The stain color was fairly consistent with a vague green tint. The stain has progressed to the point where the areas that covers over the old water line down several inches have turned dark green. Pictures are below.
I realize that letting it stay so green so long was a mistake and I will be keeping it clean year round from now on. My question is how to best clean the pool walls. I shocked the pool two weeks ago and have been brushing the pool but the stain remains. Algae blooms seem more common. Scrubbing with stainless steel brush has no effect. I also rubbed a puck on it for several seconds with no effect. Using a pumice stone did clean most of it up but I can't use that for the whole thing. Would an acid wash, pressure washing or something else be the best course of action?