Winter and Fall FAQ

The Most Asked Questions About Fall and Winter Pond Prep

What time of year should I give my pond a good cleaning and what are the basic steps?

Late fall, while you prepare your garden for winter, or early spring are the best times for cleanings. Drain your pond with a pump placed in the deepest area of the pond. Place your fish in a separate container of pond water, remove all plants, and clean out any debris that has collected at the bottom of your water garden. Refill your pond with fresh water and return all plants. Before adding your fish back, give them a chance to adjust to any change in water temperature and treat the water to remove any chlorine or other harmful additives.

If your pond is stone-lined, clear a location of gravel in the deepest area of your pond to place your pump. Using a regular garden hose with a jet spray attachment, wash any collected sediment down between the rocks to the low area where your pump can pump it out. Collect and discard any leaves, stems, twigs, etc., that may have collected on top of the stone. There should be no need to remove or replace any stone during the cleaning process. If your pond is relatively clean and the water has been clear most of the season, it is not necessary to completely drain the pond—simply drain about 75% of the water (pumping from the bottom while stirring to pull out any accumulated debris).

How do I take care of my plants in the winter?

Most hardy plants can be trimmed to about 3–6” after November 1st and placed in the deep section of the water garden. Aquatic grasses, reeds, cattails, rushes, and similar grass-like plants should be trimmed back to about 18” and placed in shallow water so that their stems rise above the surface. These plants “breathe” through their stems in the winter. Water iris should not be moved to deep water since they can suffocate if submerged more than a few inches above the pot.

How do I take care of my fish in the winter?

There are several options for “winterizing” your fish. As mentioned earlier, all feeding should stop after the water temperature falls below 43–50°F (usually around late October). Your fish require access to fresh air during long periods of ice cover. One option is to simply let your waterfall continue running, as 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. The main concern is a temporary power outage that might allow water to freeze in the line, blocking the flow even when power resumes.

What are some good basic steps to get my pond ready for winter?

• Reduce the number of leaves falling into the pond or remove them with a net.
• Do a fall pond cleaning.
• Cut back dead or dying aquatic plant foliage during the fall.
• Switch to a wheat germ-based fish food.
• Disconnect the pump, filter, and UV clarifier before water freezes.
• Store the UV clarifier indoors for protection.
• Store filters indoors if the manufacturer’s directions suggest.

What about falling leaves?

Falling leaves are hard on a pond. If left in the pond, they will decay, adding to the ammonia load and making the water too acidic. Use leaf netting over your pond during the weeks when most leaves fall. For small ponds, drape the netting over the pond and anchor it around the perimeter with rocks.

It is advisable to provide some support in the middle to keep the netting from dipping into the pond when leaves accumulate. For larger ponds, string a strong, plastic-coated wire (such as a dog run cable) between two trees or posts, drape the netting over it to form a tent, or scoop the leaves off the surface and bottom with a long-handled net.

Should I keep my pump and waterfall running in the winter?

Keeping your pump running year-round depends on the severity of the winter. If you expect a period of cold weather that will freeze your waterfall, you should turn it off. A frozen waterfall can eventually lead to water draining out of the pond.

If you decide to run your pump, raise it closer to the surface to minimize mixing colder water at the bottom with warmer water near the surface—this helps protect your fish. If your pond is prone to freezing, using a pond de-icer is recommended.

Will my fish be OK in the pond over winter?

In most parts of the U.S., it is fine to keep your fish in the pond provided it is at least 18 inches deep. Koi, Shubunkins, and most goldfish survive winter by staying inactive at the bottom where the water remains a few degrees above freezing.

Circulating water during winter can cause temperature fluctuations that may affect hibernating fish. Ensure your pond has deep enough areas (18 inches or more—30 inches in extremely cold regions) to prevent freezing to the bottom. Use a pond de-icer to keep an area ice-free for toxic gas escape, and consider bringing certain fish indoors (like fancy goldfish). Remember: do not feed your fish when the water temperature is below 42°F.

Do I need a pond de-icer?

A pond de-icer is essential for fish survival if your pond freezes over. It leaves a small area ice-free so that harmful gases trapped beneath the surface can escape. Note that most pond heaters have a built-in thermostat and will cycle on as temperatures drop.

Could I leave my UV clarifier out during the winter since it is plumbed into the system?

It is better to bring your UV clarifier indoors before freezing temperatures arrive. Running it in winter is not advisable since water inside can freeze, expand, and damage the quartz sleeve, bulb, housing, or electronics.

Should I feed my fish during the winter?

Do not feed your fish when water temperatures fall below 42°F. When temperatures are between 42°F and 65°F, use wheat germ–based foods.

When do I stop feeding my fish?

Stop feeding once water temperatures drop below 42°F. Even if the water briefly rises above 39°F during winter, do not resume feeding.

How do I take care of my hardy plants in the winter?

Most hardy bog plants can be trimmed to about 3–6” after October 15th and placed in the deep section of the water garden. Aquatic grasses, reeds, cattails, rushes, and similar plants should be trimmed back to about 18” and remain in shallow water (1–6” above the pot) so that their stems stay above the surface. These plants “breathe” through their stems during winter.

Water iris should not be moved to deep water since they can suffocate if submerged more than a couple of inches above the pot. Oxygenators and water lilies can remain in the deep section (18–36”) of the pond as long as they stay below the ice (maximum ice depth is 8–10” in Ohio). Trim all remaining leaves and stems off your lilies after the first few freezes to prevent fouling the water.