Can you move your aeration to a shallow area? If you bottom water temperature is 35 degrees, your aerator is moving too much "warm" water from the bottom to the surface.
I don't think the aeration is really the problem. If your pond loops floated to the surface then there is air in the system. Since your geo compressor is "locked" and there is air in the system I am hoping you don't have to pay for the repairs!
Systems in our area are designed to function efficiently with a 32F degree loop temperature. Our Geo contractor says he has two units that are looped in sandy soil and these will get in to the mid to high 20F degree range and still continue to produce heat.
