What Is Necessary for Winterizing Outdoor Ponds?

by Lois Lawrence

Overview

A garden pond

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Many gardeners enjoy incorporating a water feature such as a small pond in their landscapes. While natural ponds do not need any special winter care, small- and medium-sized man-made ponds do.
Removing Debris

Leaves and other debris must be cleaned out of small ponds because they release gasses that can be dangerous to fish and otherwise interfere with a healthy underwater ecosystem.

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Tending to Fish

Fish can be introduced into small, man-made ponds. What happens to them in the winter depends on the variety of fish and the climate. Consult your supplier about this. Some fish should be brought indoors; others can be traded back to the supplier in exchange for a new supply in the spring; still others do well in indoor aquariums. Fish that remain in the pond should not be fed when water temperatures fall below 45 degrees. As a general rule in moderate climates, koi fish need 3 feet of depth and goldfish need 2 feet. In cold climates, make sure the pond is at least a foot deeper than the freeze zone. Fish should not be kept in ponds that are likely to freeze solid.
Heating

There are heaters designed to work in small ponds only when the temperature approaches freezing. If your climate is relatively mild, this may be a good winter-time option for keeping water temperatures safe for most fish, though winter heating is not a necessity.
Refreshing the Water

Replace about 10 percent of the water in your pond with fresh water after the leaves and other debris have been removed and after fish that need to be removed have been relocated.

Pond Lillies

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Plants

Cut back emergent plants like reeds and cattails. Prune water lilies back to the central crown. Floating plants should be coaxed to the center of the pond where they will have the best chance of remaining ice free.