I agree with Cecil, considering your location it would not take much in terms of airflow to keep a sizeable hole open in your pond. You might also consider using garden soaker hose as your air-bubble release source, allowing you to keep a long tract of water open.
The pump mentioned has enough output to keep at least a 15x15 foot area open in my pond... which sees temps down to, or below -30 Celcius.

I have a question though... why no fish? : )

Owner/Builder of Ottawa Canada's first official off-grid home.

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