Why Don’t Fish Freeze in Ponds?

My brother threw a little feeder goldfish into his pond two summers ago. Last summer he noticed a goldfish the size of a keeper panfish swimming around. How did that tiny fish survive the winter? I researched the topic with our friends at Aquascape, Inc. Here’s what’s posted on their Popular Pond Fish FAQs.

The little fish that grew and grew.

Q. What about the fish in the winter?  Won’t they freeze to death in the pond?  Will I need to bring them in the house?

A. No. If you simply make sure that your pond is at least two feet deep, the proximity of the earth to the pond’s surface will not allow the latter to freeze any deeper than 8”.  That leaves 16” for the fish to lounge around and basically hibernate over the winter.  You do need to keep a hole in the ice using a floating heater or aerator to allow for the exchange of gasses (CO2 for oxygen).   But other than that your fish will do just fine in the pond, all year round.  Supplemental oxygen can also be supplied by running your waterfalls, adding a bubbler, or using the pump to churn the water near the surface.

Some people choose to bring their koi indoors for the winter, keeping them in stock tanks or large aquariums. I even know a couple who built a pond in their foyer so they could better enjoy their fish. We love that idea! But if you don’t want to fuss with relocating your pond fish, you don’t have to. As long as your pond is over 2 feet deep, you won’t be hurting them. Native fish in Minnesota lakes and shallow ponds hibernate every winter and awaken in the spring just fine. Mystery solved.

Hedberg carries a full line of Aquascape water gardening products and trains professional pond builders throughout Minnesota and western Wisconsin. Please call us at 763-225-0589 for a referral to a Certified Aquascape Contractor or contact us online. Be sure to visit Hedberg and the Liquid Landscapes booth #1143 at the Minneapolis Home & Garden Show March 2-6 to see fountains, waterfalls, ponds and happy non-frozen fish.

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