The covering was a great idea i thought aswell
But in this article, it say's not to cover FW planted tanks because plants start to USE oxygen when they don't have light. Since coral uses photosynthesis aswell, could be the same issue on a heavy stocked SPS tank?
http://www.peteducation.com/article....+2154&aid=2402
Heat probably would be more important in calgary's -20 winters :S, and oxygen would have to made up elsewhere.