Here in Colorado I run my aerator, a simple piece of PVC with 1/16th" holes drilled in it, 24/7 in winter. Pond is 9' deep at beginning of winter and drains down to 5' deep by spring. Bubbler device is set in 5' of water at startup in November, which becomes 1' by spring. Weeds are very abundant in fall at ice up.
Trout, LMB, BG, GSF, YP, TGCarp, assorted other oddities all survive just fine.
It's very possible the shallow water gets super cooled by this winter mixing. My fish don't take any kind of bait or lures during the winter, but arrive at the dock the next spring for pellets and mealworms. In 12 years I've only seen 2 dead floating trout and no other fish. No fungus on those warm water fish.
If it were my pond, and of course it's not, I'd run that aerator constantly in the winter, keeping a reasonable hole open throughout the winter. The hole would be close to shore so that any creature falling in could access shallow water by the bank to climb back out. One of our house cats, while prowling (looking for trouble) out on the deteriorating ice in the middle of the pond one spring, fell through. He broke ice for a few seconds, then managed to clamber back on to the surface. Oh, the looks of disgust I got when I was laughing at him as he dripped up on to the dry ground.
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