Hello all: I purchased this home with an unground pool about a month ago. It had black staining along the walls and floors of the deep end which I now believe to be black algae. The pool is an unground Gunnite Pool. I have done the following: Scrubbed twice daily with a metal brush. Treated with Black Algae killer from Leslies Pools and Black Algae Killer from in the swim active ingredient (copper sulphate pentahydrate 11.8%). SLAM shock chlorination and additional scrubbing. 1.5 gallons of Muriatic Acid followed by additional scrubbing. The areas are lightening and disappearing in places however some has now settled on the floor which is extremely difficult to get at since the pool is about 8-9 foot deep. I did all this in preparation for adding a stain removal kit but am unable to do so due to the high levels of phosphates that are now in the water. I am at my whits end trying to get rid of this stuff. After the last SLAM shock my numbers from Leslies were free chlorine 13.48; total chlorine 13.48 PH 6.8; alkalinity 9; calcium hardness 342; cyanotic acid 85; iron 0; copper .4; phosphates 1965; TDS 500; after adding the chlorine reducer and phosphate reducer six hours later my levels were free chlorine 6.16; total chlorine 6.89; PH 6.8; alkalinity 5; calcium hardness 291; cyanic acid 85; iron .1 copper .2 phosphates 1777; TDS 500. I have added photos below to show where I started and where I am now. The first three are where I started and the last three are where I am now - the staining looks deeper (darker) depending on lighting. I believe the stains are getting better but this is very slow going for an almost 60 year old woman and a two inch scrub brush.
