I'm trying to keep goldfish through this winter in a 50 gallon,
24 inch deep pond in Chicago. I know enough not to feed them. I'm
keeping the pump off so as not to force them to expend energy against
any current.

I was hoping for a mild winter, but a pretty bad cold spell has
meant a freeze-over for at least the last 35 days. I just augered
through about four inches and saw two fish of six at the surface of the
hole. I'd like to think if any are OK probably all are OK. But I wonder
if they are the only two survivors looking for oxygen.

My questions are these:
1. Do I need to make any effort to open
ice for oxygenation? Could the school have made 90 days?
2. At the end of Fall more tree leaves
got into the pond than I could control. I'm worried about their decay
consuming oxygen in the water. Will the cold inhibit the decay? Because
of the leaves, or for any other reason, should I be attempting a
mid-winter water change?

Thanks for any ideas.