I noticed that a green stain has developed around the border of the pool. My wife tried to attack it with CLR, with no luck. In fact, there is a whitish residue on the stone that doesn't seem to come off that appeared after the CLR treatment. Chlorine levels did dip when we were out of town, but the water is crystal clear, and the chemistry comes up great.
Here's a pic of the stains. This was taken with a flash, which made the Green standout more and the white wash out a bit. It doesn't look nearly as bad! Green on the bottom, whitish above. Any ideas on how to get this stuff off?