Unless you have a good reason to use a Winter safety cover, like a safety issue, why cover? I quit using my Loop-Lock years ago because it was more hassle than it was worth. Snow, melt, freeze, repeating all Winter and come late Winter the thing would be frozen in a block of ice. I keep the equipment going as long as possible and open as early as possible. As for circulation when the regular equipment is out-of-service, consider a cheapo submersible pump from Home Depot or similar place.
Al
BTW...I'm in the far Northeast corner of PA so I know what cold is too.