Instructions
Measure your pond. If your pond is less than 3 feet deep, or 4.5 feet in northern climates, it is probably too shallow to keep koi in during the winter.
Add insulation to the walls of your koi pond during construction to help the water retain heat.
Keep your filtration and pump system working in the winter if your pond is unlikely to freeze all the way through. The moving water will make it less likely to freeze.
Use a deicer. These small machines generate just enough heat to keep the water around them from freezing and cost less than $100. Select the right deicer for your pond with help from Doctors Foster and Smith (see Resources below).
Buy a heater for your pond. These can cost a few hundred dollars, but will ensure your pond's water stays at a comfortable temperature. Learn about pond heaters and how they work at Heating Your Pond (see Resources below).
Use your gas water heater to efficiently heat your pond. Connecting your pond to your water heater will be much more complicated than buying an electric heater, but could cost you less money to run. See a diagram explaining how to use your water heater at USA Koi (see Resources below).
Remove your koi from a pond that will freeze completely in the winter. Place the koi in an indoor pond or even an aquarium until the weather warms.
How to Keep a Koi Pond From Freezing
Koi are remarkably sturdy fish when it comes to cool temperatures, but to keep them thriving, you'll need to keep your koi pond from freezing during the winter. There are a few easy ways to make sure the koi you spend so much time caring for and admiring make it easily through the winter.