Keeping Pond Fish in Winter

Written by david roberts
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Keeping Pond Fish in Winter
Pond fish like Koi can survive winters if you take proper care. (Koi pond image by windzepher from

Keeping exotic fish in a cold climate presents a unique challenge. For example, if the pond is too small, it will freeze solid from top to bottom and kill the expensive fish. A specific procedure will keep your pond safe and fish alive during a harsh winter, but it takes preparation throughout the year and a little work before temperatures begin to drop for it to work.

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Things you need

  • High-protein fish food
  • Wheat germ food for winter
  • Pond cover
  • Floating pond heater

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  1. 1

    Feed your fish with a high-protein diet during the summer. The high-protein diet will help the fish build up extra fat to help them survive the colder weather. During the fall leading up to the winter, as the temperatures begin to drop, use a wheat-germ-based feed because this type of food is easily digestible. Specialised pond shops and online stores sell spring and autumn food or cold-weather-formula diets. When the water gets close to freezing, cut back on the amount you are feeding them, and when it begins freezing, stop feeding them completely.

    Keeping Pond Fish in Winter
    Pond fish need a good layer of fat to survive harsh winters with no food. (koi image by Earl Robbins from
  2. 2

    Clean out pond waste before winter. Leaves, algae, fish waste and other organics continue to decompose even under a frozen cap of ice. This decomposition process releases dangerous gases, like hydrogen sulphide, into the water that will kill your pond fish long before the freezing temperatures will. A pond filter helps take care of a small portion of the waste, but you still need to remove the rest of it with nets and pond scrapers. Raised-roof canopies direct rain water downward instead of collecting on the top and sinking the top cover into the pond.

    Keeping Pond Fish in Winter
    Larger populations of pond fish mean more pond waste. (koiteich image by photosite from
  3. 3

    Purchase at least one floating, 1kW water heater. If you have a larger pond, purchase two. These devices float aimlessly around the pond and kick on a heater when the temperature drops below 4.44 degrees C. They won't necessarily keep the pond ice-free, but they will ensure that there are areas that won't freeze over.

    Keeping Pond Fish in Winter
    A pond heater can keep your pond alive in the winter. (Japanese koi carp image by Geoff Hobbs from
  4. 4

    Protect the fish from predators. During the winter, fish have a slower metabolism and can be exposed to danger from raccoons, birds and other animals. An underwater hide box will keep them out of harm's way. You can also employ a "Scarecrow," which uses motion detectors to spray any predator with water, scaring them off. You will need to add a heater to the spray unit in the wintertime to prevent the lines from freezing.

    Keeping Pond Fish in Winter
    A raccoon or other predator will make a meal of your £58 pond fish. (raccoon image by masteraz from

Tips and warnings

  • If the pond has iced over, do not break the ice because the shock waves from the impact can kill your fish. Use warm, but not scalding, water to melt a hole in the ice, and pry the ice apart to leave a hole. Insert a floating heater into the hole, and let it do its job.

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