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Winterizing Your Pond

Pond Treatments
Pond Treatments


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For many gardeners, overwintering fish can create a great deal of anxiety, but with some helpful advice, it can really be quite do-able. You can choose to leave the fish outdoors if you have an in-ground pool or pond, or you can choose to take your fish indoors. When the water temperature reaches 42 degrees, goldfish and koi will go into a natural state of hibernation. At this point, if you wish to overwinter your fish outdoors, you can remove the pump from the pond, and stop feeding the fish. Goldfish and koi are naturally cold-water fish, and as long as the pool or pond does not freeze solid, the fish will do fine.

The necessary depth of the unfrozen section varies with the severity of your winters, but for most cold-weather areas (USDA Hardiness Zones 4 through 6), a depth of 3 to 4 feet in at least part of the pool is usually sufficient. Check with your local pet store to determine which zone you are situated in. As a safety precaution, you can add a floating cattle water trough heater, de-icer or pond heater, which has a built in thermostat, to keep at least a section of the pond from freezing solid.

If your pond is 2.5 feet to 3 feet, and you plan on leaving your fish outdoors, then you need to insulate your pond by adding straw or styrofoam, as well as plywood around and over your pond. (Do not, however, completely cover the surface of the water as this will cut off all oxygen for your fish.)

One of the main problems associated with overwintering fish outdoors is that if the ice freezes across the entire surface of the pond, noxious gasses resulting from decomposing leaves and other organic matter in the water may begin to buildup in the pond. These gases can be lethal to the fish. Therefore, it is paramount that a hole be created in the ice to allow for air exchange (please see tips below).

Alternatively, goldfish and koi can be brought indoors in the fall, once the weather turns cold. They can be stored in an aquarium or a child's wading pool. Small wading pools come in fiberglass or plastic, however plastic pools may need to be treated, because plastic residue can be toxic to fish. To treat a pool, fill it with water and add 1 tablespoon of salt per gallon of water. Let it sit for a couple of days, then wash it out and add fresh water. Remember to treat tap water with a pH conditioner. The pH level of your household water should be the same as that of the outdoor water. If the difference in levels is drastic, the shock can kill the fish.

Winterizing a Pond and Leaving the Fish Outdoors

Green Tip:

Don't spray your driveway, sidewalk, deck or porch with either your sprinkler or hose. If it's dirty, use a broom to remove dirt and dust.

Winterizing a Pond and Bringing the Fish Indoors