Winter and Fall Pond Care Guide

Getting your pond ready for winter in the fall. Brrrrrr!!

Hardy Plant Care

Most hardy bog plants can be trimmed to about 3–6” after October 15th in Northern climates and placed in the deep section of the water garden. Aquatic grasses, reeds, cattails, rushes, and similar grass-like plants should only be trimmed back to about 18” and remain in shallow water (1–6” of water above the pot) so that their stems rise above the surface of the water. These plants “breathe” through their stems in the winter. Water iris should not be moved to deep water since they can suffocate in water more than a couple inches above the pot.

Oxygenators and water lilies can stay in the deep section (18–36”) of the pond through the winter. As long as they are below ice level (maximum ice depth is 8–10” in Ohio, for example), they should overwinter fine. Trim all remaining leaves and stems off your lilies after the first couple of freezes to prevent them from fouling the water as they are shed.

Tropical Plant Care

If you have tropical plants, you can bring them indoors as houseplants over the winter or discard and replace them next spring. Most will do well in a pan with water near a bright window. Umbrella palms do especially well indoors over winter. Tropical water lilies and floating plants are a challenge to overwinter and are generally replaced each year unless you have access to a greenhouse that stays 65–75°F year-round.

Any tropical plants you wish to save should be moved to a warm location before the first frost. Floating plants killed by frost should be immediately removed so that they do not add to the plant debris in your water garden. Tropical plants should not be placed back into the water garden in the spring until the water temperature reaches 65–70°F (usually late May in northern climates).

Fall Fish Care

If you have been feeding your fish regularly, continue doing so into the fall as long as they eat the food quickly (within a few minutes). Once water temperatures fall below 60°F, it is best to switch to a wheat germ–based food that is easier to digest.

If you have not been feeding your fish earlier in the season, it is suggested that you feed them a wheat germ–based food (we recommend Blue Ridge Cool Wheat fish food or Sho Koi fish food) during the last few weeks of fall to help build additional fat reserves before winter.

In addition, Sho Koi fish food has the added benefit of a patented immune system–enhancing supplement that strengthens your fish before winter. A medicated food for parasite or bacterial infections is another good preventative step if you have had recent problems with your fish.

In any case, all feeding should stop after the water temperature falls below 50°F—usually around November 1. Even during warm spells, do not feed your fish over the winter months, as their metabolism slows down and they will not properly digest the food.

Fish Have to Breathe Too!

Your fish require access to fresh air during long periods of frozen ice. You may let your waterfall continue to run as it has all season (although there are better options). The moving water will not freeze and will provide the necessary air exchange. Even in severe cold, ice may form over the moving water, but the flow will not stop.

However, there are concerns with this method: a temporary power outage might allow water to freeze in the line, blocking the flow when power resumes; and in severe winter, ice dams can form on a waterfall or stream, causing water to back up and start a leak that would not occur in the summer.

For these reasons, if you expect to be away from your pond for extended periods over the winter, consider one of the following alternatives:

One option is to disconnect the pump from the waterfall (or use a separate pump of 175 gph or larger) and place it on a shelf about 6–8” below the water surface with the outlet pointing up so that it creates a bubbling, mini-geyser at the surface. When plugged in, this moving water helps prevent the surface from freezing completely. Even after a power outage, when the pump is turned back on, it will quickly melt through any ice that has formed. Ensure your pump still has a pre-filter attached during winter; if your primary pre-filter can’t be used, most pumps come with a smaller built-in or attachable pre-filter that usually suffices.

It is recommended not to place the pump at the bottom of the pond, as doing so would mix the relatively warm water from the bottom 6” with the colder air above, lowering the overall water temperature and possibly stressing your fish.

A second option is to use airstones to provide air exchange. Products such as Pond Aerator 2 or Pond Aerator 4 by Aquascape are good choices for small to medium ponds. The air pump is placed outside the pond, and the airstones are set on a shelf (about 12” deep) or suspended off the bottom at a depth of 12–15”. The bubbling from the airstone provides enough water movement to keep an open air hole with minimal energy cost, except in the coldest winters.

A final option (our recommended choice) is to replace the pump with a floating de-icer during the coldest months. Simply set the de-icer in the pond, plug it in, and it’s done! A built-in thermostat will turn it on when the water temperature drops below freezing and off when not needed. This is likely the most trouble-free approach. If you have a heavy fish load, a large pond, or a pond that hasn’t been cleaned well, the addition of an aerator (in addition to the de-icer) is highly recommended.

Saving on the Utility Bill

To save electricity, a de-icer need not run continuously. Simply place the de-icer in the pond with the plug hanging outside near an outlet. During extended periods of ice cover (5–7+ days), plug in the de-icer for 2–3 days to allow any toxic gases under the ice to vent.

If you have a low-wattage de-icer (under 300 watts) or a hollow-center de-icer, leave it plugged in all winter. On higher watt de-icers or those with an exposed heating element, these units will melt a hole through the ice within 24 hours. The round shape of the de-icer prevents damage from ice forming around it when it is not plugged in.

The goal is to prevent more than 7 days of uninterrupted ice cover. A few days of ice cover in a healthy pond is not harmful; however, if your pond is relatively dirty or has an extra-large fish load, maintaining a continuous air hole with your de-icer or pump is recommended. For very heavy fish loads, an aerator in addition to a de-icer may be necessary.

Caring for Your Pump, Underwater Lights, Filters, etc.

If your pump is not in use during the winter, it can be stored in any ice-free area of the pond or in a bucket of water indoors until spring. Any underwater lights should be moved to an ice-free area, or pulled out and set along the edge (out of water) until spring.

UV (ultra-violet) lights are especially susceptible to damage from ice forming in their chambers and bursting their delicate bulbs or quartz sleeves. It is important to disconnect and drain your UV light unit thoroughly before heavy freezes. Store the unit in a dry location where it won’t freeze over the winter.

Pond de-icers with exposed heating elements should have any hard water deposits cleaned from the elements before storage. Usually, wiping the element with a soft rag after soaking it overnight in vinegar will do the job.

Cover it Up

We highly recommend placing a net over your pond in the fall before heavy leaf drop. Stretch the net over the pond and secure it with stones, stakes, or whatever is available. If a heavy load of leaves causes the net to sag, simply scoop them off with a broom or hand net.

You might notice your water discoloring (turning a tea color) from the pigments of the leaves; this is harmless and will dissipate once the leaves are removed. The goal is to prevent leaves from collecting at the bottom and fouling the water.

If you have trees with very small leaves (e.g., Locust), choose a net with smaller openings (3/8” or less). We even offer leaf nets with domed supports to keep leaves completely out of the water.

What Not to Do

A few words of caution: never use a hammer, stick, or similar tool to break a hole in the ice if at all possible. This can cause panic among your fish, making them more susceptible to infections during winter when their immune systems are low.

Additionally, while there are many tricks to keep an air hole open for fish during the winter—such as floating rubber balls—we do not recommend relying on these methods in most winters.

Finally, Another Spring Arrives!

Once the chance of prolonged freezing is over (late March in northern climates), you can return your pump(s) and underwater lights to their regular locations. Any plants can also be retrieved from their deep-water winter bed and placed in their usual spots. Resume feeding your fish (if desired) when the water temperature reaches about 50°F. A wheat-based food is best for cool, early-season feedings. April or May is also a good time to divide pot-bound plants, and don’t forget to fertilize all your plants (except oxygenators) each spring!

Good luck and enjoy your pond!