BV,

I can empirically measure the temp differences at surface level with a
digital (very accurate) temp sensor, and do the same at the bottom (6 to 7
ft)

I've been doing this for 6 months now, and the maximum difference I've seen
is 0.2 degrees...

Of course, "wind-chill" may play a bigger role in winter, so covering up
will surely help.

Also, emperically (when talking about koi, there's always a difference) it
has been found that if in summer the total digestive organs take about 18 %
of a koi's body weight, after 3 to 4 months without feeding (and filtering)
that goes down to 3% (). This is also the reason why the mortality
rate of koi that have not been fed for a long time is so high in spring.
They have been consuming their own fat (which also contains the toxins that
somehow got into the pond), are very hungry, but just can't digest the food
that they can catch and eating actually gives them less energy (they have to
build up their organs again) than not eating (and they are already weakened
from not eating/sulking at the bottom)

Finally, you can emperically measure (again, talking koi) the difference in
growth rates between feeding or not feeding. Problem is, you can't really
feed them at temps lower than say 7°C, so you are kinda stuck with heating
the pond.

Not arguing mind you, and we should always distinguish between koi and more
"native" fish. It can be argued that japanese Koi are a subtropical (or
even tropical) fish, quite different from our native carp species (these
evolved via selection to harsher and longer winters)

Bear in mind that my fish have survived 3 winters without any
feeding/filtration, so it's not a black/white thing, but there are very good
arguments for keeping your pond/filter going 24/7/12.

Theo

"BenignVanilla" schreef in bericht
...

"Ted" wrote in message
...
I live in zone 9b, and my water temp in the winter only gets into the
low
50's. Is it necessary at that temp to turn my waterfall off? I have a
bottom drain where my external pump sucks the water from.
snip

It seems that this is a hotly contested topic. At least it was last fall
when I joined the group. OMIGOD, I've been here a year now! Yeeha. Anyway,
there are two crowds of IMRIGHTYERWRONG thought. One group believes that
once your water reaches 50ish you stop feeding and stop filtering. Without
feeding your fish will produce less waste and therefore not filtering is
OK.
In addition by circulating your water, you move the cold top water down to
the lower warm water. The other school of thought thinks the opposite,
filter your water, turn it over, stir it up, whatever.

In my experience, both schools have been successful, and I have not seen
empirical evidence supporting either argument. I for one have my pump shut
off...but...that is because my stream is still leaking, and I don't feel
like fixing it until Spring. That doesn't help does it?

BV.