shaggy911

I have a 22k gallon inground pool. I am not an experienced pool owner, but i have kept it sparkling clean every year. This year i am very busy and now I am looking at a green swamp. I am worried that this will turn into black algae and i will never get rid of it. Please help advise so i can let my kid enjoy the pool before it starts snowing I didnt open the pool until this week. There was a swamp over the 1" submerged pool cover. I bucketed the layer of algae out as much as i could and after an 1 hour I poured it into the pool, which was green anyway. I took the water to local pool store and they suggested i drain it to half and refil. I drained it to about 1/3 twice since on both occasions it did not do much good. I incorrectly ran the filter for 4 hours and then backflushed it : the drain water was dark green. It was back flushed to light green and i left it off the filter. I just replaced my filter (Sand dollar 80) and pump (pentair whisper flo - high flow rate ). I am worried i may have damaged the filter media. After the drain i did a analysis. Saturation index 0.8 TDS 400 CYA 0 Tot Chlorine 0 Free Chlorine 0 Ph 8.4 - added Muriatic acid later Tot Alkalinity 112 Tot Hardness 156 Optimizer+ 0 I added 1 gallon of Muriatic acid. I did not expect 4 pts would do much good. i was recommended to use power floc. I did this and used the entire bottle (double the dose). I have waited for 12 hours now and it doesnt look like Power-Floc did any good - it was supposed to settle all the algae to the floor but i see it suspended. Or maybe there is so much algae that some is still floating. I dont know why the store did not recommend to chlorine it aggressively. They werent sure about power floc and i would like to get more opinions rather than guesstimate at this point. In any event I have a dark green pool with algae visibly floating (like slush ice in winter). MY Plan:: Feel free to point out better approach i have a gunnite pool day 1: vac to waste as much as i can add 2 bottles of Banish (3% copper algaecide; light green algae dose for which is 1 bottle) QQQQ: Should i add more? recirculate the pool for a day (with the pentair i have it should take 4 hours to recirc the entire pool ) day 2: Chlorine the life out of it!!! 12 lbs lithium hypochlorite. I will pre-dissolve it with a power drill driven mixer; apply from the skimmer at a slow rate of 2 lbs per 2 hours. My pool floor is white/slightly blue. QQQQ: Will lithium hypochlorite be sufficient? It has 47% free chlorine. Should i try Cal-Chlor and risk higher Calcium levels? Seattle water is very very soft. day 3 and 4:: Analysis to ensure that i maintain high chlorine. QQQQ: What ppm of free chlorine should i maintain ? Repeat day 1 to day 4 until I prevail over Algae. Please post your recommendations. I know i should have been on top of maintenance, lesson learned.