Prepare your pond for Winter

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Clean up inside the pond.

Dead algae, fish waste, leaves and needles build up in the bottom of your pond. All of this will decompose during the winter months. As it breaks down, it will draw precious oxygen out of the water.

Clean up around the pond.

Leaves and other plant debris left on the edge can make its way into the pond. Insects and other harmful organisms can over-winter in the dead vegetation and wreak havoc on your pond plants once warm weather returns.

Use pond netting to catch falling leaves before they get into the pond and decay all winter.

For better support, use bamboo poles or plastic rods to hold the netting down. Clean the netting periodically to avoid the leaves steeping which can cause the water to turn brown.

Take a weekly measurement of your water quality.

The last thing you want is green algae growing in the fall going into winter. The algae will die and decompose in the pond during the winter, drawing oxygen that your fish and wildlife need to survive.

Switch to the autumn/winter formula of positive bacteria.

Cold, hardy bacteria will continue to digest the organic sludge that is left behind after the cleaning steps listed above. The enzyme packets included with the bacteria will digest larger debris like leaves and needles.

Be careful when letting ice form in your stream or waterfall.

Pond owners sometimes leave their pumps running so that water still flows over their waterfalls when ice is forming.  In fact they look forward to the unusual ice formations, which can be among the most beautiful winter scenes the pond has to offer. Be careful, though. Ice build-up can easily divert running water away from the stream or waterfall. This can quickly drain the pond, to the detriment of your fish and plants.

Some water gardeners turn off their fountains and waterfalls, taking out their pumps.

This is OK….if you do not have fish and biological filtration. Make sure the hoses are completely drained. You don’t want water to freeze in the pipes during the winter which makes them more susceptible to bursting. Cap the ends of the pipes. You don’t want furry little animals to use the empty pipe as a nice warm place to nest during the winter.

If you have a submersible pump and decide to shut down your pond or fountain for the winter, then store the pump in water and keep it where it won’t be exposed to freezing temperatures.

A submersible pump is usually water lubricated. When the water dries in the pump, it can cause the internal mechanisms to freeze or crack and cause problems for you in the spring.

Clean, dry and store any ultraviolet clarifiers, bead filters, and any motion-activated sprinklers.


The best way to help your fish through the winter is to make sure they are well-fed and healthy during the summer.

Take stock of their appearance. Make sure they’re free of disease and parasites. If they’re ill, take care of it now.

Stop feeding the fish when morning water temperatures are lower than 50 degrees Fahrenheit for a consistent week.

As colder temperatures approach, feed the fish a little less every day. You’ll gradually cut back their intake until they stop getting food at all. They’ll also let you know when they don’t want any more food.

Keep the pump running or plan alternate sources of oxygen for the fish.

Even with a pump running it is a good idea to add oxygenation with pond aerators. The air stones create bubbles that will work to keep a hole in the ice during freezes. This allows unwanted gases to escape. Don’t try to break a hole in ice, it will cause shock waves in the water that can harm your fish. If necessary, you can use a pot of hot water to thaw a hole.

Maintain your thermal layers.

Don’t let the water at the bottom of the pond mix with the water at the top. The bottom layer is warmer and it’s where the fish like to hide and hibernate. Pull your submersible pump up onto a shelf in the pond so that it’s not in danger of running dry but it’s off the bottom layer. If you add aerators to the pond then place them on a shelf or raise them off the floor onto an upside down plant basket or something taller.


Trim back dead foliage and remove spent flowers.

It’s time to remove all of the floating plants that will die off in the winter (at least here in the Pacific NW). Limit the amount of organic matter decaying in the pond.

Stop fertilizing plants about 3 weeks before the average frost date in your area.

You want the plants to harden off for the winter, which they’ll do more readily once you’ve withheld fertilizer. Even tropical plants, which you’re going to bring indoors, will benefit from a respite in food this time of year.

Take tender water plants indoors if you live in a winter freeze climate.

Before a hard freeze you should place tropical marginals in a warm, sunny room with their pots in a saucer of water, so that the water will wick into the soil and keep the plant moist for the winter. Tropical water lilies will need supplemental light and water that’s at least 65 F for the winter, as will tender waterlily-like plants. 

Certain plants, such as cannas and taros, can be left in a cool, dark place for a few weeks without any water.

As they dry down they will die back, losing their leaves, and forming a corm or tuber in the soil. This corm or tuber can be cleaned of soil and stored in peat moss or sand for the winter. Re-plant it the following spring.

Certain marginals can be safely left outdoors in the hardest of winters.

They can freeze solid provided they stay in the water in a matter that the crown of the plant stays moist. This includes water iris, sweet flag, water parsley, cattails, flowering rush, and many sedges. To overwinter these hardy souls, simply cut back their foliage to within a few inches above the crown once the leaves have withered and died. Then just leave the pots in the water in the pond.

Winter-hardy plants that cannot survive being frozen in the ice should be moved below the frost line in the pond.

This includes water lilies, lotus and pickerel rush. Wait until the plants have died back for the winter and remove their spent foliage before placing them well below the water’s surface.

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