Marla,
The first year of my pond, I overwintered them in the pond, against my daughters opinions, killed them all. Won't do that again. Now they are very happy inside and I have nothing to worry about outside.
Your fish are lucky to get well water, but with your big beautiful fish, I'd worry too much.
Here are where the big guys (relatively speaking) live.
I've got a dustpan waterfall and an airaetor in the other end.
Steve