In article , "Iain Miller"
writes:

If this is so then its obviously
not a good idea to circulate the water out the bottom of the pond in mid
winter (assuming filters use a bottom drain etc) which means the filters
really do need to be turned off....

if the water temps drops below 50 and stays there, I would turn off any pump to
your bio filter. If you have a mechanical filter, raise the pump up to a high
level of the pond so that the discharge is right at the surface of the water.
This keeps a hole open for gas exchanges and doesn't disturb the bottom water.

Karen
Zone 5
Ashland, OH
http://hometown.aol.com/kmam1/MyPond/MyPond.html
My Art Studio at
http://members.aol.com/kmmstudios/K....M.Studios.html
for email remove the extra extention