Doug,

Your question has got Phyllis and me thinking about our pond structure
and electric usage.

If your filter is closed, cutting off flow eliminates all sources of
oxygen. If your filters are open or veggie filters, the result might
be different.

Our filters include three upflow barrels and three veggie filters
(essentially small, open, 4' x 8' x 18" ponds). What happens if the
water flow to them is turned off? Our oxygenation from waterfalls and
streams will be ended and the water standing in the three upflow
barrels will be still, getting air only from the top surface of the
barrel. Will the lack of flow harm or kill the bacteria? In our
case, I suspect an hour of no flow in the veggie filters would not be
a big deal. I don't know about the barrels...but then their
contribution to the system is not crucial.

We have run our system 24/7 for over a decade with interruptions only
for power failures. The system did not die off when those
happened...even in the summer.

It would be very interesting to me to learn about the impact of time
and temperature on the effect of no circulation. Have you been able
to get any information from sources like the city sewage folk or
biologists? If your system has excess capacity and hour-off does not
degrade it too much to function or to survive, you might save money
without hurting your pond.

I am thinking that we have a lot of excess capacity with over 80 sq'
of veggie filter for a pond with about 300 sq' of surface. I suspect
we could probably save a good bit by doing the on/off
routine...especially in the winter when the bacteria are not doing
their thing.

I will begin doing some searching to learn about lack of flow and
filter bacteria. If you get some good data, please let us know. No
one would want to kill off the filter bacteria, but I suspect all of
us would be glad to save money and energy.

Jim

Have you thought about moving to a veggie filter process for your
filter?