I have a 27K gallon in ground gunite pool with PebbleSheen finish. I've maintained it all summer with BBB, and have not shocked it once (no CCs). I need to shock it now as I have my first measurable CCs, but am not sure if I need to leave the cover open while shocking it (its an aquamatic vinyl cover). I seem to recall that the sun burns off the CCs during shocking -- is that true?

Great forum. Thanks for the help.