A Greener View: Koi pond fall and winter care

Q: I was told that I must overwinter my goldfish indoors, but I know that they can survive in natural ponds over the winter. I don’t have an aquarium and there is no place to put one. I don’t want to bring them in for the winter. Will they be OK if I leave them out? What do I have to do to keep them alive in the pond?

A:

If your pond is shallow and you are in a cold climate, the fish may not survive. Inside tanks may be the only option for you. The farther north you live, the deeper the pond should be if you want fish to survive the winter. People in your local pond club or fish store will know the best depth and what to do with specific types of fish in your area.

Some people use algae-eating tropical fish in their outdoor ponds, but they start dying when the water temperature drops into the high 50s. At this temperature, goldfish will only be slowing down their eating schedule. Your goldfish will become inactive as the temperature drops into the mid-40s. Stop feeding them when the water is below 50 degrees. A pond thermometer is essential to proper fish care.

The most important water quality item to be concerned about over the winter is the oxygen level. Even though colder water holds more oxygen than warm water, there isn’t an unlimited supply. If the pond is allowed to freeze over, then the fish and other organisms in the pond could consume all the oxygen. It is essential to keep an open hole in the ice to allow for gas exchange with the atmosphere.

If the surface of the pond will freeze for more than a day or two, it may be necessary to install a pond deicer to keep an opening in the ice if you want the fish to stay in the pond.

There are several videos on koi pond fall and winter care and pond deicers on the Greener View YouTube channel that cover these topics in greater detail.