Till the experts give you a real answer, I will relay my limited knowledge that has came mostly from reading, not practical application.
Lots of people use an air pump to move the water instead of a water pump because of the energy used. Pumping air down and letting the bubbles do the work seems to be pretty energy efficient, as in low electrical bills. In reasonably deep water that is. At least that is the theory.
What you are doing sounds like it would work to me. In farm sprayer applications there is a thing called an agitator or sparger that fits in the bottom of a farm spray tank. It uses a vortex to gather in surrounding liquid and use the stream of liquid coming in from the pump to agitate the tank. These might work very well for what you are trying to do. They are plastic and fairly inexpensive. Here are some examples:
agitators My only concern would be to make sure any flow does not stir up the bottom muck and make the pond a muddy mess. So just watch where you aim water flow.
Good luck and if you proceed with your plan, let us know how it works out.
Edit: I see you beat me to it. You posted a picture of what I was talking about while I was composing my post.
