On Feb 11, 8:55*pm, hugh ] wrote:
In message , Doghouse Riley
writesThe idea that there can be a layer of warmer water at the bottom of a
pool is a myth. It won't happen in normal koi pools of around five or
six feet in depth. You'd need to have something well in excess of 3
metres.

It' snot a myth - it's a scientific fact that the density of water
increases as it cools down to about 4 C then it decreases as the water
cools further. (Hope I've got that the right way round) In this respect
water is unique. That means in a natural pond the water at the bottom
will be at 4C with the colder water at the top until it is so cold that
the whole lot freezes.
However as you say disturbing this with pumps running will interrupt
this natural protective mechanism for pond life.
Isn't nature amazing.

However a fountain will oxygenate the water and keep an area around it
free from freezing over. I suspect the fountain will freeze before the
bottom of the pond does.

I checked my pond temp yesterday and it was 6C at the fountain outlet,
with the rest of the pond frozen over. I left just a few wheatgerm
pellets around the fountain which appeared to be eaten later, after
several days of not feeding. I hope the freeze will be over today and
tomorrow, as predicted, as my pond filter needs cleaning. My pond is
quite small, roughly 3m x 2m and 1m deep but with quite a lot of
vegitation.

Doug.