Thanks so much for the info.

My whole pool is in direct sunlight almost all day, not even any trees for shade, I suspect that may have caused the problem as one area of the pool, by the ladder has less sunlight and the liner is less bleached there.

I didn't realize poly quat was primarily for maintenance, so that would clarify why it did not clear up the algae bloom.

I'm going to try shocking to 20 again and keeping a closer eye, I was only bringing it up to 25 once a day at night, so maybe that's why it didn't clear up all the way, plus I suspect I didn't get the algae completely off the ladder, another reason it may have returned. We're taking the ladder out as well to see if this helps.

Thanks again.