Preparing Your Koi Pond for Winter: Essential Steps for a Healthy Pond

As the vibrant colors of autumn foliage begin to fade and the temperatures gradually drop, it’s time for koi pond enthusiasts to shift their focus towards preparing their beloved aquatic habitat for the upcoming winter months. Just like any other living creature, koi fish require special care and attention during the colder seasons to ensure their health and well-being. In this guide, we’ll walk you through essential steps to prepare your koi pond for winter, allowing your fish to thrive and your pond ecosystem to remain balanced.

1. Clean and Inspect

Before the harsh winter weather sets in, start by thoroughly cleaning your koi pond. Remove any fallen leaves, debris, and sludge that might have accumulated at the bottom of the pond. A buildup of organic matter can lead to poor water quality and create a breeding ground for harmful bacteria. Additionally, inspect your pond equipment such as pumps, filters, and heaters to ensure they’re in good working condition. This is the ideal time to perform any necessary maintenance or repairs. Net the pond to prevent any leaves and debris from falling into the pond. Koi Pond Nets are available in store at Terra Waterscape Supply.

2. Trim and Remove Plants

As the temperature drops, most aquatic plants go dormant. Prune back any overgrown or dying plants to prevent decaying matter from affecting water quality. If you have tropical aquatic plants that cannot survive the winter, consider moving them to an indoor aquarium. However, hardy plants like water lilies can be trimmed and left in the pond at a deeper depth to survive the cold.

3. Gradually Adjust Feeding Habits

Koi fish’s metabolism slows down in colder temperatures, which means they require less food. As the water temperature drops below 50°F (10°C), start reducing the amount and frequency of feeding. Overfeeding can lead to undigested food accumulating in the pond, causing water quality issues. Eventually, when the water temperature drops to around 40°F (4.5°C), you can stop feeding your koi altogether. They will rely on their fat reserves during this period of reduced activity. See Terra’s Smart Pond Thermometer, and Cold Water Fish Food, available in store!

4. Install a Pond Heater or Deicer

To prevent the water from freezing entirely, consider installing a pond heater or deicer. These devices keep a portion of the water surface ice-free, allowing the exchange of gases and preventing potentially harmful gases like ammonia from accumulating under the ice. Proper gas exchange is crucial for the well-being of your koi. See Terra’s Pond De-Icer, available in store!

5. Maintain Water Quality

Regularly test your pond water’s parameters throughout the winter months. Even though your fish are less active, water quality remains essential. Ammonia and nitrite levels should be monitored closely, as poor water quality can stress your koi and make them more susceptible to diseases.
See Terra’s Cold Water Bacteria, available in store.

6. Provide Shelter

Koi fish need a place to seek refuge from extreme cold and predators. If your pond is deep enough, the lower levels will naturally provide a warmer area for the fish. Additionally, you can place floating objects like Styrofoam boards on the water’s surface to create pockets of warm air. These serve as shelter zones for your fish.

7. Consider Quarantine

Some pond enthusiasts opt to move their koi into a separate quarantine tank indoors for the winter. This provides better control over their environment and allows for closer monitoring of their health. If you choose this option, ensure that the quarantine tank is properly cycled and that water parameters are appropriate for koi.


Preparing your koi pond for winter is a labor of love that ensures the well-being of your fish and the overall health of your pond ecosystem. By taking the necessary steps to clean, inspect, adjust feeding habits, maintain water quality, and provide adequate shelter, you’re setting the stage for a successful winter season. With proper care, your koi fish will emerge from their winter dormancy in great condition, ready to grace your pond with their beauty once again in the spring.