Another thing to keep in mind with the windmill is that 20' depth you will require a pump that will operate at 10 psi. Be sure to check the specs of the windmill pump.

If the pond is open to the wind (not surrounded by trees) natural mixing will also help.

Not sure about your weather, but here the highest possible time for a pond to be in trouble with low DO is in the dog days of summer when it can become very hot with no wind. Or that combination and cloud cover (so lower photosynthesis and less O production from algae).

You might consider supplementing the windmill with some solar powered aeration to help cover those conditions.

John

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