Yes, I agree that the greenish tint to the water is metals - think of it this way, when the metals are yellowish brown and the pool water is blue, yellow and blue make green I see this in my pool all the time, that's how I know to add more sequestering agent. When my pool is clear but not quite blue blue it is because something is going on As for the cya - sometime when using a lot of sequestering agent it uses up cya. I am not a chemist, and I don't know the reason, but I do know this from experience. It can also use up a lot of calcium too. Just as I said, every time you add something to the water it changes something else Once the water is balanced (and metal free) it is easy to keep it up, but sometimes getting there is a big pain. Everyone's water reacts differently, because what is in the water is different than anyone else. This is why when you learn to care for your own pool it makes it easier - because the pool store is giving out information on a all encompassing situation, as well as selling chemicals. Keep up the good work, and keep us informed - I love your idea!