I have a 13000 gallon above ground pool with a vinyl liner. Last fall I got really busy with work and didn't keep up with the maintenance of the pool and it got stained from leaves and other debris that made its way to the bottom of the pool. It was getting late in the fall and cold and I cleaned it up as best as I could and closed it, but there were some stains that remained around the edges and bottom of the pool. I opened it 7 days ago and since then have vacuumed, shocked and tried to maintain proper chemical levels and remove the stains, but it's been tricky. I have shocked it twice and both times the free and total chlorine levels drop to near zero within 24-36 hours. For example, I shocked it Sunday night with 3lbs of pool life turboshock and by Tuesday I was reading zero on both. From what I have read, the loss of chlorine is due to low CYA levels, I did add 2 lbs of pool life stabilizer (powder through the skimmer) on Monday, but from what I have read, it takes a while to show up. As of today, I got these readings from test strips
Total Hardness- 698
Total Chlorine- 0
Free Chlorine- 0
Total Alkalinity- 180
CYA- 0-20 (the strips don't give exact measure, so this is a guess)
My main goal is to get rid of the stains. They are organic because I dropped a chlorine tablet and after letting it sit for a while and rubbing it around the bottom, it showed to remove the green/yellow stain. Brushing the stains does not do anything. Can you please advise me on the best course of action? I have attached pictures of the stains for better reference and can get more exact water test, but I'd have to go to the pool store. Thank you for your help.