I believe you posted that you measured the pond temp at the depth you thought the loop was at and the water temp was 35F.
Assuming the heat is available in the ground the water should be 39F which is the temp of water at maximum density. There is a full load heating capacity reduction of 12% with a change entering water temp (EWT) of 40F vs 30F. Data is from a Climatemaster Tranquility 27 5 ton Geo unit. I believe this unit is re-badged for Carrier. Setting aside the issue of fault regarding the icing. If turning the aereator off or moving it translates into an increase of 4F EWT it's going to put money in your pocket.
