I use test strips, and all parameters are in the middle of the spec. The water was NOT in spec when the red came to find a home. It took a bit to get here, but after getting the pH and total alkalinity in order, the rest fell right into place. just after a couple of days with the chemistry correct, it isn't taking care of itself. The pool is approx 44,000 gal. sand filter, and a power vacuum. I believe the pits/craters were caused by a pH imbalance way before my time. the smooth part of the plaster is just fine, but every crater is rough, and has a red deposit. If it is bacteria, a good should take care of it I would imagine. I am trying that tonite, pump off long enough to let the water stop circulating, and I'm going to pour the shock down the walls and hope it coats the sides with a concentrated solution.

Thank you all for your suggestions, and help.

Chris