i wouldn't put the cover on when shocking..it will help it deteriorate faster. a solar cover definitely works..it's not hype. last fall when it was down to 6C overnight, i only lost 1 to 2 degrees off of 26 swimming temp. the cover will keep most debris out, but some will still get in so don't count on it keeping all leaves out..but most will..when you go to roll it up, you're likely going to put some in the pool..some people before taking off spray any debris into the side skimmer with a hose . yes, the water circulates with the cover on