If you live in a colder climate, you may wonder what to do with your pond fish when your backyard oasis is at risk of freezing solid. Fortunately, with the right conditions and preparation, many types of fish can thrive through the winter months in outdoor ponds. It's important to choose a species of fish that is naturally more resilient to cold aquatic life. But the key is to set your fish up for success with an appropriate pond and proper overwintering care.
Best Fish to Overwinter in Your Backyard Pond
- Koi: These colorful fish are such a popular choice that backyard koi ponds are an aesthetic all on their own. All varieties of koi can survive in cold temperatures as long as the pond is deep enough and there is enough oxygen.
- Goldfish (Comet, Shubunkin): The common goldfish can handle a frozen garden pond surprisingly well. They may be a pet shop staple but they actually have a long life expectancy and their adaptability means they can handle a wide range of conditions as long as they are set up for success.
- Minnows (Fathead Minnow, Rosy Red Minnow): These small fish have slender bodies which makes them fun to watch dart around. They are a great choice for pond owners as they are extremely resilient and can survive the colder temperatures of an outdoor pond.
- Golden Orfe: This fast-moving fish prefers to live in schools, making them a great addition to a larger pond. They are highly tolerant of cold weather, but pond owners need to give them space and good water movement to stay healthy in the winter.
- Tench (Golden Tench): A bottom-dwelling fish that are incredibly hardy and well-suited for cold winters. They already spend most of their time feasting at the bottom of a pond, and their habit to burrow into the pond substrate makes them excellent survivors during the colder months, when the water at the bottom of the pond is warmer.
- Carp (Mirror Carp, Common Carp): Members of the carp family reliably go dormant and overwinter well. These larger fish adapt to a range of water conditions but they need space and require about 250 gallons of water per fish.
- Rudd: An often underrated community fish, this species can tolerate cold waters and are particularly active, even in lower temperatures. They are a great choice for medium to large ponds, and their vibrant colors make them visually appealing.
- Pumpkinseed Sunfish: These cold climate fish are native to North America and handle even the harshest of winters quite well. Their scales are a range of colors which make them a visually striking addition to ponds.
- Weather Loach (Dojo Loach): Named for their behavior of becoming more active when a weather change is coming. They are hardy, bottom-dwelling fish that can survive in freezing ponds by burying themselves in the substrate for warmth.
How deep does a pond need to be?
To survive freezing temperatures, a pond with fish should be at least 3 feet deep. A deeper pond provides a safe space for fish beneath the frozen surface. The deeper areas won't freeze completely, allowing fish to settle into a state of reduced activity, known as torpor, until the warmer months return.
How do fish get oxygen in a frozen pond?
Fish can still get oxygen in a frozen pond, but it requires careful pond maintenance. As ice forms on the surface, it seals off the pond from air, reducing oxygen levels. To keep your fish breathing, pond experts advise to use a pond aerator or a de-icer to maintain an open hole in the ice, allowing gas exchange. Another method is to install water features like a fountain or a waterfall to keep part of the water surface moving, preventing a full freeze.
Feeding Your Fish in the Fall
As temperatures drop, fish metabolism slows down, which means they require less food. You should gradually reduce the amount you feed your fish as the water temperature falls below 50°F. Once the temperature dips to around 40°F or lower, you can stop feeding them altogether, as their bodies enter a dormant state and they no longer need to eat. One of my neighbors (Zone 5B) feeds his fish their "last supper" at Thankgiving, having gauged that it's the latest in the season they can eat before dormancy. For reference, their pond is also almost five feet deep, and they've overwintered for more than 5 years so far.
Tips to Keep Your Pond Fish Alive in Any Climate
- Install a pond heater or de-icer: This keeps a small section of the pond surface from freezing entirely. Without a hole in the ice oxygen levels can drop, and harmful gases can accumulate stressing or even killing your fish.
- Use a pond aerator: By circulating water, an aerator helps oxygenate the pond, because moving water prevents stagnation. Even with ice forms, cold water fish will have enough fresh oxygen.
- Remove excess organic matter: Clear the pond of leaves, debris, and dying plants in the fall. Remember, not every aquatic pond plant is cold hardy and they'll die and rot as temperatures fall.
- Add beneficial bacteria: Healthy bacteria keep your pond ecosystem balanced by breaking down organic matter before the freeze. It's a great choice for backyard ponds that are particularly wide or deep.
