I've been using the BBB method all this season and couldn't be happier. I'm puzzled by a chalky residue that covers the sides of my pool. When you rub it, it comes off and floats as small "dust" particles creating a cloudiness in the water. The pool was repainted this past spring, walls are fiberglass and bottom is concrete.
Any help on identifying what this is and what to do about it would be appreciated.