As the air becomes crisp and the temperature begins to drop, you’ll notice some changes in your pond. Temperature is a factor that affects different aspects of your pond and there are certain temperatures to make note of in autumn to help prepare your pond for the winter conditions to come.
Across the US, water temperatures start to dip in September/October. Having a thermometer helps to monitor water temperature as the fall weather advances. As the water becomes a steady 70 degrees, it is recommended to perform a 10 percent water change to rid your pond of extra pollutants to keep your pond as balanced as possible for winter. The winter conditions like cooler temperatures, shorter days, and dying vegetation influence the biological and ecological characteristics of your pond. These can affect your pond’s water chemistry, which in turn affects the biology of fish and other plants and animals that dwell in your pond.
Fish are cold-blooded animals that cannot maintain a constant body temperature like humans. The body temperature of fish is affected by how cool or warm the water is, and their metabolism and activity level fluctuates with water temperature. Fish are less active in cooler water, which means they need less food than they do in the warmer seasons. Fish will generally slow feeding when water temperatures are at or below 60 degrees. When the water temperature is steadily between 55-60° F, only feed once a day and switch the food to a wheat germ based diet because these foods are highly digestible at lower temperatures. When the temperatures stay between 50-55° F, reduce feeding to once a week. If the temperature stays below 50° F, you can stop feeding them until the weather warms in spring. It is important not to overfeed because uneaten food will add excess organic matter to the pond increasing the chances of low oxygen levels and a fish kill. Discard any remaining fish food since the nutrients in any open packages will disintegrate over time. Sometimes there are warm spells during the winter seasons and fish may come to the surface. Be sure not to feed them as they may be coming up for air and any food they eat will not be digested.
Treat your pond with a broad range parasite treatment before the water temperature falls below 50°F. Any fish containing parasites over the winter will be untreatable due to the lower water temperatures. Once the temperature drops below 40 degrees Fahrenheit, turn off any running water such as fountains or waterfalls. Make sure that your pond is deep enough. As the temperature decreases, your fish will retreat to the deeper areas of the pond, where the water is warmer. The deeper the pond, the more considerable the change is. Turning off pumps is important so that colder water does not circulate to the warmer water found on the bottom of the pond where fish and plants seek refuge during the cold months.