In the beginning, and based on your picture above of open water, I would run it long enough each day to produce an open water area 20 ft in diameter. That should do what you need for your quarry-like steep sided pond.
Thank you for the advice. The hole is fully frozen over again since it's been cold and we put the aerator on a 3 hours off, 1 hour on timer. I think we'll have to make it come on a little more until we get less cold weather. We will aim for a 20ft diameter.
