I've only only had my pool for six weeks and sadly I don't use the FAS-DPD test but the strips to test. Everything was going well and with no actual numbers I've concluded that my FC is low. I didn't know what that meant until I found this "gunk" in my pool. I shocked it and I vacuumed and it came back. I also have brushed the pool and the gunk floated away like dirt particles and returned. I have a 24x52 round AGP with sand filter 1 HP. I do have the FAS-DPD test and will test tonight and in the morning. I'm attaching photos I just took. Does this look like algae although my water is clear? Thanks for reading and hopefully responding!!