After spending hundreds or even thousands of dollars on beautiful koi, carp, and goldfish, you don’t want to risk losing them all to one cold night. While many common pond fish are perfectly capable of handling anything short of freezing solid, other species are more delicate and should be removed if you aren’t going to heat the water. Supplemental heating for a pond of even just a few hundred gallons can make a noticeable increase in your energy bills over the winter. You have a few options, in addition to heating the water, for protecting your most valuable and sensitive fish during cold weather.
Build a Deeper Pond
Pond depth is the key to fish survival over the winter. The deeper the pond, the larger the zone that is left underneath any ice buildup. Leaving more water free for the fish and plants ensures that adequate oxygen remains available throughout the winter. A minimum depth of 18 inches to 24 inches is recommended in warmer areas, but the coldest regions will need 3 to 4 feet of depth to keep fish alive the entire winter. While a deep pond will still need ice breaking measures to allow gases to escape, you can trust your fish will have plenty of water to keep them comfortable as they go dormant. Shallow ponds are much more likely to freeze solid, making a depth of at least two to three feet recommended for most fishponds.
Install a Liner
Lining the pond is one of the best ways to protect it from damage over the winter. If you heat the water for your fish, the warmth will attract animals and insects that burrow into the ground below. When these dens or burrows breach the sides of the pond, leaks begin that threaten to drain the pond right from under the ice. It’s easy to miss the signs of a leaking pond when there’s ice covering most of the surface. Installing a durable pond liner from BTL Liners is the best way to keep pests and soil shifting from causing ponds leaks over the winter.
Keep Ice Clear
While it’s acceptable to let ice form over the surface of most of a pond in the winter, you must keep some of the surface clear if you have fish and plants. Toxic gases build up under the ice over the winter as waste decomposes. Fish like goldfish and koi also need to visit the surface occasionally for extra oxygen in the winter, especially at the beginning and end of the season. Pond deicers that use electricity to generate a small amount of heat are the best choice. Large ponds will need multiple units to open up enough holes in the ice to keep the gas exchange even across the entire body of water. Alternative methods like manually breaking holes in the ice aren’t recommended since the fish can be damaged by the shock of the ice cracking.
Don’t Feed
Once temperatures drop below 39 degrees F, most popular fish species like koi and goldfish go dormant and move to the bottom of the pond. They won’t eat while they’re in this stage, so don’t add food to the pond during the coldest parts of the winter. Many pond owners mistakenly think they need to keep holes in the ice cover specifically for adding fish food. However, adding food that goes uneaten will just fill the bottom of the pond with muck that ruins the water quality. There’s little bacterial activity to break down uneaten food in the winter too, compounding the problem. Track the average daily temperature and only start feeding again when entire weeks remain above 39 degrees F. Try a spring and fall fish feed based on a product like wheat germ to ease your fish into eating again without shocking the water or their systems.
Move Indoors
Some species of fish, including the most delicate ornamental goldfish and tropical species like Plecostomus, must be moved indoors when winter temperatures drop below 50 to 60 degrees F. They simply won’t survive the cold no matter how much you try to heat the water. Set up a large aquarium and give it plenty of time to reach a balanced stage of water quality before moving the fish. Even in a warm indoor environment, the tank will likely need supplemental heating of its own. Consider sticking with fish that can stay outdoors during the winter in your area, to eliminate a lot of wintertime hassle. Most koi, carp, and some goldfish can happily survive freezing temperatures as long as there are breaks in the ice and plenty of water that doesn’t freeze.
Don’t Forget the Plants
Sensitive plants are even more likely than fish to be killed off by ice, especially those that are rooted or potted right along the surface of the water. Thick ice sheets, forming around the edge of the pond, can wipe out all sorts of attractive water plants you’ve added to serve as hiding places and food for your fish. Keeping your most sensitive plants potted allows you to quickly remove them in the fall and relocate them indoors to a basic aquarium. Even if the fish stay in the pond, consider setting aside some indoor space for water plants that might not make it through the winter.
With care and some extra equipment, most pond fish can stay perfectly healthy in a pond with minimal heating. Focus on keeping ice cover from closing off the surface and design the pond from the start with appropriate depth. Using a BTL Liners product to line the pond is also recommended so water isn’t lost from under the ice while it’s hard to notice.
