in article , Dave at
wrote on 21/10/02 12:56 PM:

Mark Kelly writes

I know this will have been covered before but...

My 3 foot deep, 6000 litre pond is about to start it's first winter.

My water temperature is 5 Celsius and the fish have started to slow
down.

When should I turn off my pump/UV and what else should I be thinking
about.

I use 10°C as my guide. Once the air temperature reaches that I stop the
pump and the waterfall for the winter. The water then cools and settles
into stable thermal layers, the bottom (densest) never going below 4°C.
The oxygenating plants in the water do the rest, and the many fish have
lived and bred happily for a number of years.

If you leave the pump on when it gets cold, then you will ensure that
all levels in the pond are reduced to the same outside ground
temperature.

I removed unwanted plants and dead matter earlier on when it was a bit
warmer (for me), but I'd leave them be now and do it in the spring.

I don't feed the fish much anyway, but even less now, and not at all if
I can't see them moving actively. I also don't break the ice or fuss
about keeping it clear. To be honest, it rarely lasts more than a few
days at a time, even if thick enough to walk over. No-one clears it on
natural ponds.

I don't think that having a pump running in a pond is going to make any
difference to what the water temperature is. For a pond to be effected by
'layers' in the winter it's probably going to need to be in the in the
region of about 100ft + deep. For a 3ft deep pond the water surface temp
will be the same as the bottom temp whether the pump is running or not. If
anything having the pump running will prevent the ice forming where the
water runs back into the pond.