Fish are often the main reason that people choose to have a pond installed in their yard. People aren’t likely to sit and watch their tulips blow in the breeze for hours on end, but a pond owner will most definitely gaze upon their fish for extended periods. It’s a relaxing and soothing activity. As a pond owner who loves their fish, you’ll want to ensure you take care of your finned friends through the winter months.
Have no fear! As long as the pond does not freeze to the bottom and an air hole is provided on the pond's surface, your fish will survive the winter. If your pond is at least two-feet deep, the proximity of the earth to the pond’s surface will keep the pond from freezing any deeper than eight inches. That leaves 16” for the fish to lounge around and hibernate over the winter.
Use a pond de-icer to maintain a hole in your pond’s ice and allow for the exchange of gasses (like oxygen). Supplemental oxygen can also be supplied by running your waterfalls, adding a bubbler or aeration kit, or using a pond pump to churn the water near the surface.
Your pond fish will become dormant during the winter once water temperatures drop below 50 degrees F. This is also the point at which you should stop feeding them. Fish will feel hungry in cold water, even down to the mid 40's, however the enzymes needed for the digestion of most koi food will be lacking. The fish will eat, sometimes fully, and then languor in the cold water as their metabolism slogs the food through. In very cold water, fish simply don't eat.
Take care of your koi and pond fish during the winter months to ensure a healthy life for them well into spring and beyond.
Read more about caring for koi and pond fish.