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Preparing your Koi Pond for Winter

Pond Lighting

When you have fish in your backyard pond, winter pond preparation and care becomes a little more complex than ponds without fish. You have to worry about their well-being, which includes figuring out if you need to bring them inside for the winter, what water treatments they may need, if/when you need to stop feeding them, and what equipment you might need, such as air pumps and de-icers. When it comes to caring for your koi fish during the winter, consider these supplies and options:

  • Putting koi in a fish tank in the house or garage (a necessity if your pond is less than 18” deep)
  • Using a pond de-icer
  • Using an air pump

A general rule of thumb in terms of when to shut your koi pond down for the winter is when your pond water drops below 50 degrees F and stays at that temperature for 10 to 14 days. This is when you will stop feeding your koi fish as well. Once you stop feeding them, do not resume feeding until you have consistently warm temperatures in the spring, regardless of whether you get a random warm spike for a few days before then. Why stop feeding your koi fish?

  1. Metabolism. The metabolism of your koi fish slows down significantly once the temperature dips below 55 degrees F. This means they are unable to digest their food and it winds up sitting in their digestive tract, where it will rot and ultimately end up killing them.
  2. Waste. If the temperatures warm up for a day or two and your fish are able to digest the food, what happens if the temperatures drop right after? Their waste will produce dangerous ammonia in the pond water that will not be broken down properly.

Choosing a Tank for Indoor Storage

If you decided to host your koi fish indoors, you’ll need a tank that is 100 to 1,000 gallons in size, depending on how many koi fish you’ll be housing. A Polytank or stock tank is recommended as they are more durable and portable than classic glass aquariums.

Garage storage – if you decide to store your tank in an unheated garage, you’ll need a de-icer and small filter.

Home storage – if you keep your tank in the house, or if your garage is heated, you’ll need a filter as well as pond fish food. Your fish will be warm enough to maintain regular activity if being kept in a heated room.

A few tips for indoor storage: Cover the tank with pond netting to ensure your fish don’t jump out, set it up near a power source, water source and drain, and regularly change the water.

If you decide to keep your koi fish in their outdoor pond, you’ll need a de-icer and an air pump.

Pond De-Icer

pond de-icer is an essential device for ponds in regions that tend to experience freezing winters. By maintaining an opening in the ice to allow the proper gas exchange to take place, a pond de-icer keeps koi and other pond fish safe.

Air Pump

A pond air pump offers supplemental aeration for fish ponds and water gardens that can help create a healthier aquatic environment. Air pumps are often needed in the winter months to maintain adequate oxygen levels when the main pond pump is shut down.

In addition to a de-icer and air pump you’ll need a few other items for winterizing your koi pond. Leaf netting to block fallen leaves from your water, a thermometer, and water treatments will come in handy during this time of year.