I have a gas heater as well as a solar cover and my wife and I prefer pretty warm water (79 degrees). Gas is expensive and it is a pain to constantly take the cover on and off. I typically run the pump on a timer overnight and manually turn on when we are swimming in the day. The cover seems to work really well as an insulator for night but I'm not sure if it is better for heating during a sunny day or if just open sunlight works best. If I leave the cover on with a sunny day, I notice the first few inches of water is VERY warm, but underneath it is chilly. Is it better in that case to circulate the water while the cover is heating it?