Winterizing Your Pond

Winterizing your garden pond is a vital annual task that can begin in late September or as soon as leaves begin falling in your area. However, the job is best done at intervals through the late summer and early fall. It is a lot easier to convince yourself to do the bulk of the winterizing then rather than waiting until the water is freezing cold.

Save the last minute, small things for the late fall or very early winter, but whatever you do, try not to put it off too long.

Here are some strategies for proper and easy preparation for cold weather.

Begin by removing as much organic matter from the bottom of your pond as possible, including leaves from pond plants, tree leaves, decaying or live algae, twigs, silt, etc.

Here's the part that will be the most time consuming and messy so leave this job for a nice warm autumn afternoon! Siphon off the bottom of your pond with a simple gravity siphon, straining larger debris with a net. Never remove more than about thirty percent of your pond's volume at a time. (Use the dirty water on your perennials and shrubs; it'll be a treat for them!)

If you have trouble starting your siphon, or have a simply impossible stretch of hose to start by huffing and puffing on it, use a utility pump to start the water flow. Place the pump in the pond and hold the end of the hose over it until gravity takes over. By the way, this may sound like a No-Brainer, but make sure that the hose is pointing downhill so gravity can have an effect!
When the temperature in your pond begins to drop to about 65°, start feeding your koi a low protein, high carbohydrate food. These foods are often sold as 'fall/spring' diets for koi.
Stop feeding koi when the temperature stays at 50° or below for a week or more. A thermometer makes this job much easier!

Stop feeding your water plants about three weeks before the expected first hard frost. September 15th is a good stop date to use in Central Illinois.

As the first few frosts kill back your lotus, lilies and other pond plants, remove the dead foliage before it can decay in the pond. Place the trimmed-back plants in the deepest part of the pond where they will overwinter.

Remove tropical plants before the first frost. Most tropical and marginal plants can be kept as house plants in an oversized deep saucer near a sunny window. Tropical waterlilies require specialized care, see our page on Wintering Tropical Waterlilies.

Most water plants and pond fish must remain unfrozen to survive winter. Placing a pond heater that is advertised as safe for plastic ponds in your garden pool is the best way to ensure that your pond will not freeze solid.
Plants such as rushes, reeds, horsetails, and cattails can be frozen solid with no problems; leave them at the water surface for decoration. Drop all other plants to the bottom.

Cold water holds much more oxygen than warm water, so do not worry about your fish suffocating. Enough oxygen enters through the opening created by the heater.

Make certain your power outlet is correctly wired for a device such as a pond heater. Most pond heater 'failures' are due to insufficient wiring, which either continuously trips the breaker or the ground fault circuit. This seems to always happen during the coldest weather when the heater is drawing the most electricity. If you choose a heater over 1000 watts we strongly recommend that you have a qualified electrician check the outlet!

Place fruit tree, or pond netting over your pond to prevent more leaves from blowing in and decaying over winter.

Make sure to use a cold water bacteria preparation such as MicrobeLift Autumn PrepTM in your pond to aid in filtering and removal of decaying debris. Use String Algae BusterTM as needed during cooler weather.

Remove all electrical equipment from your pond (such as underwater lights) and store them indoors in a dry place.

Decide whether you want to keep your pond's waterfall running all winter. Depending on your exposure (micro-climate), and the severity of the winter, you may well be able to do this in this area. If you remove your pump(s) keep them in a bucket of water over the winter so that the seals do not dry out and crack.

Never shatter or break ice in a pond when fish are present. The shock from the impact can seriously injure or kill your fish.

Decaying organic matter left in a pond over winter robs precious oxygen from the water, and creates an ideal place for anaerobic bacteria to flourish. This leads to the increased probability of bacterial infections in spring as the pond warms up. You can never be too vigilant in making sure as much of this as possible is removed.