Your Pond in Winter
1: Winterizing your pond
2: Overwintering pond fish
3: Why can't I just let nature take care of my pond in winter?
4: Caring for aquatic pond plants
5: Pumps and filters
by Brett Fogle
A series of five pieces reprinted, with permission, from different issues of Pond
Stuff, newsletter of http://www.macarthurwatergardens.com
of Baton Rouge, Florida
1: Winterizing Your Pond : Cool Tips and Advice for
For many parts of the country, it's getting to be that time of year again. Time to start
thinking about getting your fish and plants ready for old man winter...
Every year, as the weather gets colder and we start heading into winter, many of our
customers ask us how to prepare their ponds for winter. Pond owners should be aware of
several simple things to do in preparing their ponds for colder months.
Fish and plants need very different things in the winter, but can be kept in top
condition for the following season if the appropriate steps are taken (see related
Fish should be fed less, floating annuals should be thrown out, potted hardy plants
should be cut down and moved to the bottom of the pond, filters should be cleaned &
drained, and pumps shut off.
Another good practice that we recommend is to do a partial pond cleaning and water
change. It's not necessary to drain the pond completely, but we recommend draining 25% -
50% of the water and net out or remove as much organic debris as possible (i.e. leaves,
The reason for this is because rotting leaves, dead plant material, and other organic
wastes will give off toxic gasses as they decay during the winter. This can be especially
dangerous if the pond is allowed to freeze over.
A thick layer of ice can easily form over the pond in sub-freezing temperatures, which
can prevent these gasses from escaping from the pond. If allowed to build up, your fish
will suffer. The most likely result will be a weakened immune system, and a more
vulnerable fish you will have come spring time.
Anything you can do to reduce stress on your fish prior to and during winter, will pay
off handsomely in the Spring. Your fish will be much more vibrant and healthy.
Another important reason not to let your pond ice-over is because the oxygen levels in
the pond water can drop to dangerous levels. By keeping the pond surface from freezing
over, or by at least keeping a 2' - 3' hole in the ice, you can eliminate or greatly
reduce these dangers.
Oxygen levels should be maintained during winter if at all possible. If you have a
standard aquarium air pump - plug it in outside and let it run all winter.
We also recommend maintaining your salt levels during winter. This keeps your fish's
slime coat strong, and immune systems strong all winter long!
2: Overwintering Pond Fish
The metabolism of koi and goldfish is controlled primarily by water temperature. As the
water cools, pond fish require less protein in their diet. When koi and goldfish are fed
high-protein food in cool water, the excess protein is excreted as ammonia from the gills.
The microscopic organisms that make up the biological filter (and consume ammonia) also
slow down in cooler water.
Improper seasonal feeding can lead to a build-up of toxic ammonia, which stresses fish
and reduces their winter survivability. When the water temperature drops to approximately
65░ F, start feeding with Spring & Autumn Pond Food. This type of fish food is better
suited for the dietary requirements of pond fish in cool water and wont pollute the
water with excess ammonia. Some water gardeners continue to feed their fish until they no
longer come to the surface. I stop feeding my pond fish when the water falls below 42░ F.
There is no need to worry about "frozen fish" if a section of the pond is at
least 18 inches deep. Pond fish will seek the deepest part of the pond and over-winter
there until the water warms in the spring. If your pond is less than 18 inches deep, the
fish may freeze during a harsh winter. Check with your local pond supplier if you live in
an area with harsh winters.
Some water gardeners with shallow ponds attempt to keep their koi and goldfish in
kiddie pools or aquariums set up in a cool basement or garage. This is not recommended
because of the extra stress involved in netting, transporting, and re-acclimating the fish
to the new environment.
However, if you don't have a choice, and need to bring your fish inside for the winter,
be sure to have an aquarium air pump or small fountain to provide oxygenation. The fish
should be fed infrequently, if at all, depending on the water temperature. pH, ammonia and
nitrite, which should be monitored weekly and especially if the fish are fed.
Small water changes (20%) each month will keep the water in good shape until spring.
Koi are "jumpers"- so be sure to cover the pool with bird netting!
3: Why cant I just let nature take care of my pond in winter?
All summer long, youve enjoyed the tranquility of the water garden-beautiful
foliage, sounds of trickling water and colorful fish eagerly awaiting a handful of food.
The water garden didnt get that way by itself. You added the right kinds of
plants and fish to create a balanced ecosystem. The water gardens we create look beautiful
and sustain life because we follow natures rules. Its the same during the
Despite all outward appearances, the pond is active even when the water is cold or even
frozen. Dead leaves, algae, insects and solid fish waste that have accumulated over the
summer slowly break down during the winter months.
This natural decomposition uses oxygen and produces small amounts of hydrogen sulfide,
a toxic gas that normally never reaches a harmful level. Few water gardeners realize that
the pond must be balanced in winter too. Fish, frogs and other aquatic life are especially
sensitive to poor water quality in winter.
A build-up of leaves and other organic matter can cause an imbalance, reducing oxygen
to dangerously low levels and releasing poisonous hydrogen sulfide.
One autumn I decided to see how well nature would take care of my two ponds. I let the
lily leaves die back naturally, falling into the pond. Leaves and sludge covered the
bottom of the pond. What could go wrong? It looked natural.
Come next spring when the ice melted, I was shoveling out black, stinky ooze garnished
with dead snails, frogs and my prized fish. I learned my lesson well. Now I use a coarse
net to remove dead leaves. I also use a fine weave aquarium net to remove sludge. You can
reduce sludge build-up with bacterial "cleaning" products for water gardens.
4: Caring for aquatic pond plants
Long after the impatiens have been pulled out, water gardeners are still hoping for
that last lily bloom.
For some reason, we want to squeeze every leaf, bud and blossom out of our aquatic
plants before winter. Unfortunately, cold weather often comes before weve trimmed
the cattails or pruned the lilies. Wait too long and all those beautiful leaves will fall
off and rot in the water. Trim bog and marsh plants such as papyrus, taro and cattails,
before frost hits.
Pull out the hardy water lilies and trim off all the leaves. Yes, even that last bud!
Put all the potted plants into the deepest area of the pond to prevent freeze damage.
Tropical lilies wont survive the winter and are often treated as annuals,
discarded in autumn. Some water gardeners have saved tropical lilies by storing them in
Trim off the leaves and roots and cover the rhizomes in a tray of damp (not wet) peat
moss. The peat moss has antiseptic properties and helps inhibit rotting of the rhizome.
The tray of peat moss should be kept in a cool basement or garage and sprayed with
water periodically to prevent drying out. Inexpensive submerged plants, such as Elodea,
Anachris and Cabomba should be discarded as well as floating plants like water lettuce,
and water hyacinths.
5: Pumps and filters
You wont need to filter the water but its a good idea to keep it moving at
the ponds surface.
Pond life needs oxygen even during hibernation. If ice covers the surface of the pond,
oxygen cant get in and toxic gasses cant get out.
Submerged pumps with fountains or waterfalls will oxygenate the water and keep a
portion of the pond from freezing. If you live in an area that freezes solid I recommend
using a pump and fountain to aerate the water.
Set the pump on bricks about one foot below the water. This will prevent the pump from
getting clogged with leaves.
If your fountain output appears to be diminishing, check the pump to make sure it is
not clogged. Floating pond heaters are available to keep a small area free of ice.
You can also use an aquarium air pump and diffuser stone to oxygenate and prevent ice
formation. Even if the pond completely freezes over, the air pump keeps pumping oxygen
into the water.
Brett Fogle is the owner of MacArthur Water Gardens and several
pond-related websites including macarthurwatergardens.com and pond-filters-online.com.
He also publishes a free monthly newsletter called PondStuff! with a reader circulation of
over 6,000 pond owners. To sign up for the free newsletter and receive a complimentary
'New Pond Owners Guide' for joining, visit http://www.macarthurwatergardens.com