My intent here is to get some insight on a system gone wrong. We had a pond loop placed in our pond during construction of our home a couple years ago. The installer designed a system with three coils of 500', 1 1/2" pipe. The coils are about 1 1/2 ' high by 4' by 4'. All told with the run between the coils and the house there is about 1700' of pipe. The depth of the pond is about 15' where the coils are. The system works great in the summer but the compressor freezes up in the winter. Incoming temps to the compressor range from 40 to 36 degrees when the pond is frozen over. The installer is suggesting we replace the coils with slinkys across the floor of the pond. Maybe it will work. I do not want to go through another winter living on kerosene heaters. I brought in a pond managment consultant to measure the temps at the bottom of the pond while it was frozen over because the installer did not have any equipment. The readings were all 40 degrees on the floor. As soon as the equipment was raised off the floor the temp dropped to 35 degrees. The consultant told me that due to the physics of the water as it freezes the water in a frozen pond will be too cold to run a geothermal loop in the winter. As I understand him and physics, the water stratifies with the coldest water on top, water that is about 35 - 33 degrees on the bottom and water that is above 35 degrees is in between. The only reason that the water on the floor is 40 degrees is because of the ground temp. Is the consultant right? Will an iced over pond produce enough temp to run a geo heat pump? Any insight is greatly appreciated.