Last week I wrote about an intractable green-water problem. This weekend I did some more reading, more testing, and more thinking. While the water was a dark green, there was no visible algae, and nothing was slippery. So I took the water into the pool store and asked that it be tested for iron and copper. Sure enough, there was copper in the water. I bought some Pool Magnet Plus, and over the course of the weekend poured in 28 ounces (7,000 gal pool).
The other problem I'd been experiencing was low filter flow. The pool guy sold me some filter clearing stuff, but that didn't help. Pressure was about 15 psi. Then, just for the h of it, I opened up the lint pot. Guess what? A thing called the anti-syphon rotor had rotated so that it was covering about half the intake tube. We straightened it out, put the whole thing back together, and pressure shot up to 25 psi!
By the next day, the water was a pale green color, and I was one happy pool owner.