Hi, We live in the country and I have
an old cement livestock tank that I am using for a fish pond.
The pond is 1000 Gal, about 3 feet deep, round, and is about
½ above ground. I have had this as a pond for about
10 years.
Every winter we cover the pond with an insulated plywood cover
and put in a tank heater. Most winters we lose our koi. The
goldfish seem to survive. What can we do differently? Should
we keep our filter pump running all winter? And change the
level of the flow of water? (I have read that circulating
the water will bring the
warmer water up to the top and the colder water down) We thought
about putting bales of straw around the tank and on top of
the cover. Does it need to be kept warmer for the Koi?
I trim back the plants that I have and drop the pots to the
bottom for the winter. Do you have any experience with this
type of tank/pond and how we can manage it? I have mainly
been doing things by trial and error but have had fun watching
the pond and working with it. Are there any specific articles
to read that would be helpful for me?
Hi Nancy,
I think that there are a few things
you could do to improve things.
1) Rather than covering the pond with
solid plywood, I'd use an open framework covered with plastic
poly-house material. The five or six-degree difference you'll
get from passive solar heating makes a big difference.
2) A high-capacity air pump and airstone
to keep oxygen levels in the water up will help. It'll also
keep the water from freezing over.
3) Right around Labor Day each year,
get your fish into a holding tank and clean out your pond,
getting rid of as much of the organic crud on the bottom
as you can. During the winter, this stuff breaks down and
generates noxious gases.
4) Look at your stocking levels. You
may have more koi than your 1000 gallons can support.
5) Get yourself some high-efficiency
biofiltration during the ponding season to maximize the
health of your fish. A pond that supports healthy fish through
the summer is more likely to deliver live fish through the
winter.
6) There's no real benefit in keeping
your pump running through the winter unless you are heating
your pond above 45 degrees on a consistent basis.
