I'm new to this forum, and will be trying to keep my pool clean with the BBB method once I get it clean. I opened my pool 2 weeks ago, it was pretty green. I could barely see the bottom of the 3" shallow end - (FYI 35,000 gallons IG). Lots of shock & 10 days of constant filtering and backwashing left me with very cloudy water. I couldn't see the bottom drain in the deep end. At forst I thoulght it was due to high alkalinity - was 180 - brought it down to 110. Now I have the following TC 3.0, pH 7.2, Alk 110. Based on strips (I know now- do not use), -0- FC no matter how much I put in. Per leslies- everthing is perfect, safe to swim. After finding this forum, I used my HTH test kit and found that my CYA level is more than 100. Just finished dumping about 2 feet of water and am refilling. I wil be ordering a Taylor test kit today. What really concerns me are these purplish stains that are on the sides of my liner, most of them circular. They do not come off when I brush them. I have attached a cell phone pic, since that's what I had. Is this an algae? has anyone experienced this before?