Thanks, Kurt! No, we don't have a vacuum. I will test the water first thing in the morning - I see that several things getting out of line allowed the algae to gain a foothold. I'm going to take the water to the supply store of the company that built the pool and put in the ozonator. Other than selling me chlorine, they've been pretty good with advice - not trying to up-sell me like the Warehouse Pool guys always do.

Do the shock granules also add more CYA to the water? I have the in-line feeder also and the dial up to about 4. I realize that most of y'all do not ue the pucks and maybe after this is fixed, I will have the confidence to go with just the BBB method.

Is there NO way to lower CYA other than draining the pool? If I don't add any more tri-chlor, will the level eventually drop on its own, what with rain, adding non-chlorinated water, etc.?

Thanks a lot for your help!