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Hi Bob:
I have subscribed to the Water Gardening Magazine for the
last several years. I belong to the Capital Area Koi and
Water Gardening Club in Lansing, Michigan.
I have had a pond with goldfish for about 30 years. I joined
the Lansing Pond Club about 6 years ago and acquired koi.
I had water lilies in the pond from the beginning.
I have a albino catfish who is approximately 20 inches long
and a lot of koi who are approximately 16 inches long. And
some goldfish.
We put a new pond in this summer (about 2500 gallons) with
a falls and stream as the smaller one was getting quite
crowded and I didn't want to get rid of any fish. I also
have a filter system made from a 100 gallon horse tank,
will have two next summer (got the pond in late this summer).
I know everyone has different experiences with their koi ponds.
I wondered what your idea was on keeping the filter and pump
running in the winter. I had always shut the pump off in the
old pond and used a small pump to keep a hole open for air.
Thanks for listening. Any ideas are welcome.
Sincerely,
Marilyn
Hi, Marilyn,
Your instincts are excellent. Water increases in density as
it approaches 39 degrees F. As it gets colder than that and
begins to freeze, it expands and becomes less dense, which is
why ice floats. Koi will tolerate water temperatures down to
37-39 degrees without undue stress and become more stressed
as temperature drops below that. Since their effective metabolism
slows drastically at these temperatures, any undue activity
other than cruising slowly around the bottom will stress them
and waste their stored energy.
Keeping the falls running when
the air temperature is below freezing not only maintains constant
water movement and mixing, but will also create a source of
"supercooled" liquid water which can achieve sub-freezing temperatures
and remain liquid as long as it is still moving. This will severely
stress your koi, and they will be much more prone to problems
in the spring.
Your filters should be drained and the feed lines
blown out as much as possible. You won't get any bioconversion
at temperatures below 45 degrees, and they are likely to freeze
and rupture when the weather turns really cold if they are full
of water.
Water over a falls in Michigan winters will also tend to freeze
in areas of slower flow, and can divert the entire volume of
your pond into your yard in an hour or two, leaving you with
a large hole containing koisickles.
By all means, continue to shut down your pumps as the weather
turns cold. Cover your pond with a greenhouse construct to keep
the wind and debris out and dangle a large airstone hooked to
a high-capacity air pump about a foot below the pond's surface.
The shallow turbulence created in this way will keep the water
surface open and will not disturb the deeper stratified layer
of warmer water where your fish will be gathering. Air pumps
tend to be more reliable than submersible water pumps, and can
be hidden under a bucket or something to protect them from the
worst of the winter weather.
Bob Passovoy
President
MPKS
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