Bruce the colder the water the fish are in,, the less solids they will produce due to eating less food thus water changes would not have to be as frequent nor as much. As mentioned earlier I would try to have the water mostly above 50F-55F which will keep the biofilter active and the fish will feed a little better and that may result in a little fish growth or at least they will maintain good body condition over the winter.
I am installing an insulated hood or cover for this system this weekend. Hopefully this will allow me to gain an extra ten degrees to get into the fifties. I really hope I can achieve this, because I agree that this will allow for some real growth. It's easier to justify an entire winter's work if you can see at least a tiny bit of growth. It just "feels" better.
Holding a redear sunfish is like running with scissors.
