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Most pond keepers in this area keep cold water fish. Some examples are comets, shubunkins, orandas and koi. If you added tropical fish during the season, they should be moved to an indoor aquarium during the early fall. Most cold water fish can winter in the pond, assuming that your pond is at least 24" deep in the ground and you give a little attention to late season clean-up. Fish metabolisms slow down when the water temps fall below 50 F. Therefore, they require less oxygen and little or no food. (It is also true that colder water holds more oxygen than warmer water, requiring less oxygenation.) Fish continue to graze on the algae on the walls of the pond, but cannot digest complex foods such as commercial fish food.

STOP FEEDING your fish when the temp. falls below 50 F.

HARDY WATER PLANTS live in the garden pond year round. They die back like terrestrials. Trim stiff stems above the water. Most hardy plants can winter at the same depth in your pond as you have them during the growing season.

- MARGINAL PLANTS with leaves that grow up out of the water, "emergents" (e.g. Iris, Rushes & Sedges) can typically freeze solid and come back bigger and stronger if you leave them high where they can get the sun's early spring rays.
- EXCEPTION - PICKEREL RUSH, although rated hardy to Zone 4, winters more predictably if TOP of the pot is dropped to 9" or more.
- WATER HAWTHORNE & WATERLILY CROWNS do not want to freeze. Be sure the TOP of the pot is at least 12" below water level.
- LOTUS GROWING ENDS dive to save themselves as water temps cool. Be sure the BOTTOM of the pot is 18 - 24" below the water level.

ZONE 6 PLANTS include Thalia dealbata, Marsilea (all 4 leaf-clovers), Pennywort, Parrot Feather, Golden Club, Floating Heart, Dwarf Aquatic Bamboo, and Arundo donax. These plants can stay in the pond for the winter. Clip the foliage as it dies back, clean up the pots and drop them, the top of the soil WELL BELOW THE 12" FREEZE POTENTIAL.

TROPICAL PLANTS will not winter in your pond - thus you have basic choices:

-Treat them as annuals- that is, remove and discard them, knowing that you will buy new next year.

-Treat tropicals as you do your house plants and be sure to bring them inside before the first frost.

Many people enjoy setting up a small indoor water garden in the house to winter their tropical water plants. Tropical Waterlilies can be overwintered in a greenhouse or well-lit indoor ponds -or- by storing the tuber until it is time to sprout it next spring. See our handout “Wintering Tropical Plants” for more information.

FOR MORE INFORMATION CONCERNING PLANTS, their preferences, and plant and pond care in both the growing season and in the fall and winter, consult our Water’s Edge “Water Gardener’s Guide and Plant List”.

DREDGING & CLEANING are important fall activities. Decay of debris uses oxygen and produces gases which are toxic to fish. In the growing season this is no problem, as these gases dissipate into the air. In winter, an ice mass can prevent the escape of these gases.

This may include full pond cleaning, but most often means netting out accumulated debris and removing the dead and dying foliage.

DOSE YOUR POND regularly during the cool season
with cold water beneficial bacteria to consume organic waste.

dredging and cleaning

NET YOUR POND before heavy leaf fall to keep added organic material from getting into the pond. Tent the netting, using a stable netting pole base or other structure. Cover the entire pond and secure the sides of the net with pins, bricks or stones. The net will shed the leaves off to the sides of the pond where they can be collected. Netting can usually be removed after you have cleaned up the leaves in your yard (typically between Thanksgiving and Xmas).

can double as a winter bubbler base - Our Winter Handout demonstrates ways to keep an area of the pond's surface open during the cold months, preventing fish kills.



In preparing for winter, Zone 5 pondkeepers either leave pumps and filters up-and-running - or - turn them off. You might make your decision based on the frequency with which you visit your pond in the winter and how much water you have moving through the air.

The 3 major risks of keeping systems running are:

  • Structural damage on waterfall stonework due to freeze/thaw cycles and the weight of all those beautiful icicles.

  • Creating ice dams which divert the water outside the system. Long streams are prone to this kind of problem, particularly when exposed to blowing leaves which can aggravate the situation.

  • Accelerating temperature changes. Rapid temp changes can be stressful to fish and other aquatic organisms. The more water you move through the air (tall or high volume falls and/or long streams) the more quickly the overall pond temperature changes.

Another consideration is what will happen to the pond and equipment if/when there is an extended power outage.

Regardless of your chosen winter methodology, here are some definite to-do's before heavy frost (Thanksgiving is usually safe):
  • Turn off all auto-fills/float valves AND their water source and clean them up. Remove or blow out all related shallow plumbing.

  • Pull all ultraviolet filters (both in-line & inside skimmers) and their related plumbing, clean them up, and store them inside for the winter. Be sure to blow out all related lines.

  • Drain all other In-line filters such as pressure filters and bubble-bead filters and blow out related plumbing. If present, check bypass plumbing connections to make sure they are winter tight.

  • Give your pumps and intake filters (screens, boxes, and skimmers) a good cleaning and flush out the lines to remove sediment.

  • Clean out your biofilter, even if you plan to keep the system running. Late fall, when water temps drop into the 40's, is the perfect time! Nitrifying bacteria go dormant during the cold season so the 'bio' part of the filter is not working. Take this opportunity to rinse all mats and other bio-media and get the sludge out of the settlement chambers. When water temps begin to rise in spring, your filter will be ready!


Skimmers- pull all brushes and mats out so they don't ice up- since fish are not feeding and plants are not growing, there is less debris. Run the skimmer with just the basket or net to catch the 'big stuff'.

Keep a de-icer anchored close to the skimmer mouth for 'insurance'- to prevent ice build-up around the skimmer entrance.

Biofilters- After cleaning, return filter media to the biofilter, or store inside for the winter.


Lower the water level below perimeter stonework. This will help avoid structural damage, i.e. spawling and fractures caused by freezing and thawing.

TURN OFF your fountain or waterfall. Leave in-pond pumps & filters on the floor of the pond, or remove them altogether. DO NOT store where they can freeze.

Skimmers- after servicing brushes, mats, nets and baskets, place them back in the box. Remove the pump discharge assembly and place them on the bottom of the pond. No pumps or related plumbing should be in the top 9-12 inches of water. Keep the skimmer full and the door open.

Biofilters- Drain and blow out the line from the biofilter on down. Clean and store filter media either back in the biofilter or inside for the winter.

BUBBLER PUMPS are a good alternative to waterfalls and fountains. A small pump with a PVC riser creates a 'gurgle' at the pond's surface and keeps part of the pond open for the winter, allowing toxic gases to escape. This adds winter interest and also provides a water source for birds and other "critters". Position the pump so that

  • The intake pulls water from the mid-depth area (e.g. 9-16" below the surface) leaving the warmer bottom water undisturbed.

  • You can easily reach the intake screen / filter for periodic cleaning.

  • The riser just reaches the surface of the pond

AIR PUMPS connected to air stones or diffusers can also be used. This method is preferred for heavily stocked koi ponds which benefit from added aeration during both summer and winter months. In winter, the air bubbles keep a hole open in the ice, allowing toxic gases to excape. PLace airstones and diffusers toward the water surface for a more concentrated area of focus. In summer, diffused aeration is not only good for the fish, but it also aids beneficial bacteria and deters algae growth. Place air stones and diffusers on the bottom of the pond for a wider area of focus.

Air pump

Protect the air pump from the weather, and place it above water level to prevent flooding the pump
if the power fails!




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