I don't know how thick the ice on your pond could get, but one winter I was
on Wickiup reservoir, SE of Bend, and cut a hole through the ice. It was
about 20" thick. That was in January as I remember.
Anyway, don't 'break' a hole in ice that forms, as the shock of doing so is
detrimental to the fish at near freezing temps. Instead keep a hole open all
the time by having an aquarium air stone bubbling 24/7 in your pond. The
hole doesn't have to be very big at all, a few inches even.
Don't feed the fish at all when WATER temp is below 55 degrees, they'll be
fine. At temps below 55, their digestive systems basically shut down, and
any feed that they eat rots in their system, very possibly killing them.
I have a friend that lives in Lapine 30, miles south of Bend, that has a
pond. He simply keeps a small hole open and lets the rest of the surface
freeze over. When the snow builds up over the ice, you can't even tell where
the pond is.
Hope this helps.

Paul