The Importance of Keeping Your Pond at the Right Temperature

While it may seem surprising many pond fish, including Koi, catfish, bluegills, and minnow, are able to live in ice covered ponds in their natural conditions.

When a small pond contains many fish, however, they are likely to die if covered with ice for a significant period of time. A small percentage of the pond cover will need to be kept ice free to allow for the transfer of gases and prevent your fish from dying.

There are heaters with thermostats available for purchase that are specifically designed for this purpose. Pond fish become more vulnerable to disease when they are under stress, and water temperatures below 65 degrees (18 degrees C) can put a lot of stress on pond fish. Another significant cause of disease in pond fish is a quick and extreme change in water temperature. If you really value your fish you are going to want to keep the water temperature above 65° throughout the winter. For most people in the United States this will require installing both insulation and heaters in their pond.

Water chilling devices, such as fountains and waterfalls, should be turned off in the winter to reduce heating costs. There are several different types of materials that can be used to insulate a pond, including greenhouse structures, pool covers, Styrofoam sheets, and plastic sheeting. Keeping the pool covered is an important step as the water temperature in the pond drops as water evaporates from the pond.

As much as 80% of total heat loss from open ponds can be attributed to evaporation. Remember that the insulation will probably need to be removed on very warm days. Your fish can be shocked by the excessive heat which can result from leaving the insulation on during a hot day. Some people will prefer to transfer the fish inside for the winter, into a tank with a re-circulating filter. Your pond will be easier to drain and maintain if you decide to transfer your fish.

To keep your outdoor pond at the correct temperature you will need to calculate the heat loss in terms of BTU per hour per square foot of your ponds surface. This number will be approximately 15 times the difference between the coldest average air temperature and the desired temperature in your pond. Let’s say the average daily temperature this fall was projected to be 35° and you wanted to keep your pond water at a comfortable 65°, a difference of 30 °. Let’s also assume that surface area of your pond was 100 by 15 square feet.

Using the numbers from above we can calculate the needed BTU at 45,000. You can reduce that heat loss up approximately 80% by insulating your pond. There are many different options when it comes to heaters. The most cost effective choice is probably a gas heater similar to those used in hot tubs and pools. Another good option is an immersion heater which has been approved for outdoor or submersion use. Many of these are electric flow types.

Many fish species are not compatible with either copper or copper nickel piping, so these materials should be avoided. It may be possible, however, to use them with either titanium or stainless steel heat exchangers. To avoid bio fouling the water should always be filtered prior to entering the heater.

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