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 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 over-winter 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 over-winter and are generally replaced each year unless you have access to a greenhouse that stays
65-75 degrees year-round. Ask for our handout: “Over-wintering tropical lilies” for other tips. 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 water temperature reaches 65-70 degrees (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
continue to eat the food quickly within a few minutes. Once water temperatures fall below 60
degrees, 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 your fish a
wheat germ based food (we recommend Blue Ridge Cool Wheat fish food or Sho Koi fish food) the last
few weeks of the fall to help them build some additional fat reserves before the winter. In addition,
Sho Koi also 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 that may be useful if you have had recent problems with your fish.
In any case, all feeding of the fish should stop after the water temp falls below 50 degrees- usually
about November 1. Even during warm spells, do not feed your fish over the winter months since their
metabolism will have slowed enough not to properly digest the food even though they may seem
Fish have to breathe too!
Your fish do require access to fresh air during long periods of frozen ice in the winter. You may let
your waterfall continue to run as it has all season, (but there are better options). The moving water
will not freeze and will provide the needed air exchange. Even in severe cold, ice will form over the
moving water, but the flow will not stop. There are a couple of concerns with this option: First: a
temporary power outage might allow water to freeze in the line blocking the water flow even when
power resumes. Second: in a severe winter ice dams can form on a waterfall or stream causing water
to back up and start a leak that would never occur in the summer.
For these reasons, if you expect to be away from your pond for extended periods over the winter, we would suggest one of the following alternative methods.
One option is to disconnect the pump from the waterfall (or use a separate pump 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 water surface. When plugged in, this moving water helps prevent total
freezing of the surface. Even after a power outage, when the pump is turned back on it will quickly
melt through any ice that has formed on the surface. Be sure your pump still has a pre-filter attached
to the inlet during the winter. If your primary pre-filter can’t be used, most pumps come with a smaller built-in or attachable pre-filter that will usually suffice.
It is recommended that you do not place the pump in the bottom of the pond since you would be
mixing the relatively warm water in the bottom 6” of the pond with the much colder air above-
lowering the overall water temperature and possibly stressing your fish.
A second option is using airstones to provide a source of air exchange. Pond Aerator 2 or Pond
Aerator 4 by Aquascape are good choices for small to medium ponds. The air pump is placed outside of the pond and the airstones are placed 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 for very little energy cost in all but the coldest winters.
A final option (our recommended option), is to replace the pump with a floating de-icer during the
coldest winter months. Simply set the de-icer in the pond. Plug it in, and you’re done! A built-in thermostat will turn it on when water temperature drops below freezing and off when it is not needed. This is probably the
most trouble-free approach. If you have a heavy fish load, large pond or pond that has not been cleaned well then the addition of an aerator (as well as the de-icer) is highly recommended.
Saving some Electricity $$$$
To save some electricity, a de-icer need not run all the time. Simply, place the de-icer in the pond
with the plug hanging outside of the pond near an outlet. During extended (5-7+ days) periods of ice
cover, just plug your de-icer in and run it 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 then leave the unit
plugged in all winter. On higher watt de-icers or de-icers with an exposed heating element, these
units will melt a hole through the ice cover within 24 hours. The round shape of the de-icer will
prevent any damage from ice forming around it when it is not plugged in. The goal is just to prevent
more than 7 days or so of uninterrupted ice cover in your pond. A few days of ice cover for a healthy
pond is not harmful. However, if your pond is relatively dirty and/or has an extra-large fish load,
we recommend maintaining a continuous air hole with your de-icer or pump. In fact, for very
heavy fish loads, an aerator in addition to a de-icer may be needed.
Caring for your pump, underwater lights, filters, etc.
If your pump is not being used over the winter, it can be stored in any ice free area of the pond or in
a bucket of water indoors until the spring. Any underwater lights should be moved to an ice-free area
also, or they can be pulled out and set along the edge (out of water) of the pond till 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 & drain your UV
light unit thoroughly before any heavy freezes. Store the light in a dry location where it will not
freeze over the winter. (UV lights can normally run undamaged through frost, but should be disconnected before temperatures fall below freezing).
Pond de-icers with exposed heating elements should have any hard water deposits cleaned from the
elements before storing. Usually wiping the element with a soft rag after soaking them 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! Just stretch
it over the pond and secure it with stones, stakes, or whatever else is handy. If a heavy load of leaves
cause the net to sag, just scoop them off with a broom or hand net. You may see your water discolor
(turn a tea color) from the pigments of the leaves-this is harmless and will dissipate after the leaves
are removed. Your goal is just to prevent those leaves from collecting in the bottom and fouling your
water. If you have trees with very small leaves (Locust etc.), choose a net with smaller openings (3/8”
or less). We do offer leaf nets with domed supports to keep leaves completely out of the water.
What not to do
A couple words of caution. Never, use a hammer, stick, etc. to break a hole in the ice if at all
possible. This can cause a panic to your finned friends, making them more susceptible to an infection
during the winter months when their immune systems are very low.
Secondly, there are many other little tricks you may read or hear about to keep an air hole open for
fish during the winter. Suggestions such as floating rubber balls, etc. all may be effective in a mild
winter but we would not recommend to you to depend on them in most winters!
Finally, another spring arrives!
Once the chance of prolonged freezing spells are past (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 regular locations. Resume feeding your fish (if desired) when
water temperature reaches about 50 degrees. A wheat based food is also best to use for cool, early season
feedings. April/May is also a good time to do any dividing of pot-bound plants and don’t forget to
give all your plants (except oxygenators) an application of fertilizer every spring!
Good luck and enjoy your pond!