Koi fish pond

Your pond is lovely throughout the Spring, Summer and Fall months of the year – but if you live in an area where the temperatures dip below freezing during the Winter, then you need to put some time into preparing your koi pond for the winter months. Just how much winterizing you’ll need to do is dependent on your climate, your budget and your koi pond itself.

If you live in an area where the temperature only slips below freezing for a couple of days at a time, you may not need to do anything at all. Fish are cold-blooded creatures, and nature has equipped them with their own defenses to the cold. When the water temperature starts to drop, their metabolism slows and they use less oxygen and require less food. In areas where your koi pond won’t freeze over completely, the biggest concession you’ll have to make to the cold is to alter your feeding routine. The kois’ slowed winter metabolism can’t handle food well at all.

If your climate is more severe, but not severe enough to freeze the pond through, then your main problem will be to make sure there is some oxygen exchange between water and air. You can best do that by preventing the pond’s surface from freezing over completely. There are a few different ways of accomplishing this.

- Keep the water moving. Keep your water pump or filtration system active through the winter. Moving water is far harder to freeze than still water. Anything that breaks the surface tension of the water will help with this – a fountain in the center of the pond, your normal filtration system or some other sort of agitation system. Be careful not to let the pump get frozen in.
- Heat the water. In line water heaters are another way to prevent your koi pond from freezing. They can be a very expensive option, though – not only the cost of the equipment, but the cost of running the equipment.
- Open a hole in the ice to allow oxygen transfer. Be careful how you do it, though. Breaking the ice can send shock waves through the water that will damage the fish’s delicate systems. Instead, use hot water to melt a hole in the ice.
- In extreme cases where your koi pond is likely to freeze completely, bring your fish inside through the winter, keeping them in large aquariums.