yeah, I put a plastic tent over my pond in the frozen tundra zone 5. but I put my
pump into a bucket filter and hang that inside. it both filter crud outta the water
and oxygenates well enough and keeps the surface of the water ice free all winter.
best is it will work even if we have a power outage for a while and the pond does
freeze over. Ingrid

"Iain Miller" wrote:

I was just thinking about one or two things & was wondering what happens to
the oxygen levels in the pond over the winter if all the
filtration/circulation is switched off. I know the fish go very quiet & hang
out down the bottom but surely the water down there gets pretty oxygen
depleted? As I understand it water is actually at its most dense at about 4
degrees C (39F) so in the height of winter its quite likely that the pond is
actually warmer at the bottom than the top. 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....

What's the general concensus - how do the fish survive in an oxygen depleted
environment?

I.




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