On Wed, 18 Jan 2006 22:49:44 GMT, Roger wrote:

AIUI water is at its most dense at 4C so ice forms on the surface.
However given a severe enough frost you fish pond would freeze
solid.

It would have to be a pretty hard and long frost to freeze a decent
fish pond solid in this country.

As you say water is most dense at 4C, so it sinks to the bottom of the
pond. As the surface of the pond gets colder it gets *less* dense and
floats on the 4C water below. Convection stops and the only way the
lower water is going to freeze is by conduction, ice is a pretty poor
conductor of heat and the lower levels are in the relatively warm
ground as well.

--
Cheers
Dave. pam is missing e-mail