First, you must establish the groundwork for healthy fish by preparing
your pond correctly in the fall, including doing an aggressive cleanout
of the pond. Good fall maintenance means less loss of fish by
maintaining better water chemistry, as well as less chances of fish
coming down with bacteria/parasites in the spring, when fish are
weaker from overwintering. See sidebar, right, for a simple chart with
temperature recommendations for winterizing your pond in fall.
There are four vital actions for successfully keeping your pond fish
healthy over the winter in any climate: enough oxygen and gas
exchange, feeding your fish correctly for the temperature, appropriate
depth so that fish can get to warmer areas of the water, and ensuring
the fish don’t become stressed, so they'll be healthy in the spring.
The number one reason fish die over winter is due to a lack of oxygen.
A good way to prevent this is to test your water regularly. Regular
testing provides crucial information regarding the health of your
pond. Before you winterize your pond, perform a comprehensive
water test, using a kit like the Master Liquid Test Kit. Another essential
test is for oxygen itself, which you can test with the Pinpoint
Oxygen Meter to determine current conditions. Monitor any parameters that are
awry and take steps to rectify the factors that contribute to them.
To ensure there is enough oxygen in your pond in winter, your
pond must have proper gas exchange. There are several
things you can do to make sure oxygen is adequate.
||Install a deicer to keep a hole thawed
at the top of the ice so that gas exchange can take place.
||Put in an aerator. We suggest the KoiAir Aeration Kit, which includes tubing, compressor, and more, so you don't
have to buy everything separately. Aeration is one of the safest
ways to provide water circulation, as it creates little water
movement (see the section on fish stress to learn why this is
||Keep winter-hardy plants, like zone-appropriate bog
plants or non-tropical water lilies, inside the pond to
emit oxygen and use up carbon dioxide.
Even though your fish need to bulk up for winter, be careful not
to overfeed. Starting when the water temperature reaches about
70°F, gradually reduce the amount of food you are feeding. Feed
2-3 times a day what they'll eat in 5 minutes or less, then remove
any excess food. Gradually add lower-protein (wheat-germ-based)
foods, like our Spring & Fall Diet to your fishes' staple
diet when the temperature of the water reaches about 60°F. When
the temperature reaches 50°F, you should be exclusively feeding
wheat germ foods, as the bacteria in a fish's digestive system
are no longer able to process food efficiently. Once the water
temperature falls below 40°F, you should stop feeding your fish.
Fish must have a place to go when the water in the pond freezes.
If you have ever been in a lake in the summer, you know that
the deeper you go, the cooler the water is. Well, in the winter,
this process reverses, so that as the depth increases, the water
gets warmer. This process is a form of temperature inversion.
To help this process, you must provide a deeper area where the
fish can find refuge. The needed depth of the area depends on
the minimum temperature in your zone, and can range from 18"
to 9 feet deep. Knowing the frost line in your zone is vital. Your
local garden shop, extension service, or building inspectors will
know where the frost line in your zone is. Above the frost line, the
temperature gets colder than 32°F, and below, it will generally stay
above freezing. As a general rule, the deepest area of the pond
should be at least double the depth of the frost line, to be safe.
Don't stress the fish
Stress causes immune systems to falter, affecting fish health. There
are a number of ways you can keep your fish stress-free in the winter.
One way is not to overstock your pond, so the fish don't compete for
space. Another is to minimize water movement where the fish are.
The fish will be resting at the depths of the pond, and movement of
the water there causes them stress, because they'll be using vital
energy to keep their bodies stable in the moving water. If you use
an aerator or any other kind of agitating equipment in your pond
over the winter, use lower gph to ensure that only the top part of the
water is moving. Also, NEVER use a hammer or other instrument
to crack a hole in the ice as the vibration will also agitate the fish.
These four points are essential to keep your
fish healthy in winter so your aquatic life is
in good physical condition when it's time
to open your pond fully in the spring.