Can't Get Rid of Green!!

[chem geek]

My best guess is that your chlorine got used up over the winter and the PolyQuat 60 lasted for a while and then also got used up. When that happened, the algae could take off. Also, bacteria consumed the CYA producing ammonia which made for nice algae food (algae need nitrogen -- typically from nitrates, but ammonia will do nicely).

JohnT is right that without any measurable CYA any chlorine you add will get cut in half in about a half hour in direct noontime sun. I suggest you add Dichlor granules/powder since that will add both chlorine and CYA. You don't want to add too much. It takes 3 pounds of Dichlor per 10,000 gallons to raise the FC by 20 ppm and the CYA by 18 ppm. So I would add enough Dichlor to cumulatively add about 20 ppm of FC since the 18 ppm CYA should be enough to keep the chlorine from burning away too quickly (you can always add more later). Look at this post for some brands of Dichlor if you don't know of any.

Then, hit the algae hard with bleach or chlorinating liquid, maintaining the FC level at a minimum of 10 ppm FC though you could target 15 ppm to make things go faster.

JohnT may be very right that you have copper that has precipitated at the high pH which would make any gray/white cloud (of dead algae) look green. However, the dead algae should filter out and breakdown from the chlorine if you run the filter 24/7, expose the pool to sunlight, and keep the chlorine level high (you might clean the filter, especially if you see a rise in pressure). If your pool doesn't start to clear in 48 hours, then we can look at other things. By the way, what is your CH level? Maybe the TA, high pH and a high CH has your pool cloudy from calcium carbonate.

Richard