On Wed, 03 Sep 2003 13:52:39 GMT, wrote:

the air temp is going to determine how deep the frost is going into the ground.
everyone in the "north" depend to a very great extent on the warm earth (55o) keeping
the water liquid. if the frost goes lower than the depth of the pond it is going to
be like trying to keep an above ground pond thawed. bocu electrical bills. Ingrid

I do not think that the frost line in the ground necessarily reflects
the ice depth in the pond. The difference is that the pond water
moves. Water gets to its maximum density at 39 degrees F, 7 degrees
above freezing. So there is a constant exchange between top and
bottom. That does not happen in the soil.

The end result is that pond ice builds much slower than soil freezing.

JMHO

John