Let's try this again...
Pool at the top of a Building in Mexico City during the recent earthquake. While the water looks very clean, it is NOT a "Trouble-Free" pool.
I can't believe the guy just stayed in the water!
One question first: Do you own a Maytronics pool cleaner? The cord on mine is beginning to disintegrate and it is producing blue sticky Crud.
I agree it certainly could be Copper Algaecide as posted above. Just trying to give you a potential alternative.
While the pump is rated for 3700 GPH, I expect with lift it will be closer to 3000 average. 2 pumps could do 6000 GPH, that is a LOT of flow! That would drain my pool in about 4 hours!
One pump should drain your pool in about 4.5 hours.
Post some photos of Sunsets/Sunrises or Moonshots. Here is my pool with a sunset in the background.
My Wife and I do a 2 mile walk around the lakes (flood retention ponds) in our neighborhood. Here are some sunset shots over one of the lakes.
1 HP pump on Amazon. I've been using this for my pool since my 1/6 and 1/3 hp both seized up. I have not had to drain since joining TFP. I used the pump for aeration recently. It moves a lot of water. Pair it with a large 2-3" flat hose and you'll move some water. It is rated up to 3700 GPH...
You are running 65% on the Salt Cell. I have a 25,000 gallon pool. Maybe you should run more hours at less time. I run 24 hours a day at about 25% and I'm further south with stronger sun.