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A Guide to Keeping Koi in Winter: Ensuring Health and Vitality During the Frosty Months

Posted on November 08 2023, By: Lydia Lucas


Koi carp, with their captivating colours and elegant swims, have become a favourite amongst many pond enthusiasts in the UK. However, during the chill of winter, caring for these ornamental fish can pose its own set of challenges. It's crucial to understand and provide what they need as temperatures plummet.


Here's a detailed guide to help ensure your koi remain healthy and vibrant throughout the British winter:

Understanding Koi Metabolism in Winter

As cold-blooded creatures, koi's metabolism slows significantly when the temperature drops. This means they require less food, and their digestive capabilities are diminished.


Feeding Koi in Winter

  1. Switch to Wheatgerm-based Foods: Unlike high-protein diets used in summer, wheatgerm is easier for koi to digest in colder temperatures. These foods are specially formulated for winter feeding. Have a look at our Wheatgerm Pellets here: https://www.walterproducts.co.uk/collections/fish-food/products/walters-wheatgerm-pond-fish-food-pellets-spirulina
  2. Reduce Feeding Frequency: As the temperature drops, you'll want to reduce the frequency of feeding. Once water temperatures descend below 8°C, it's advisable to stop feeding altogether. Overfeeding in cold temperatures can lead to undigested food rotting inside the fish, causing health problems.
  3. Monitor Water Temperature: It's a good practice to have a pond thermometer. This way, you can closely monitor the water temperature and adjust your feeding schedule accordingly.


Water Quality and Aeration

Maintaining good water quality is essential. Decomposing leaves and waste can lead to the build-up of harmful toxins. Ensure you:

  1. Use a Pond Net: Regularly clear out falling leaves and debris from the pond.
  2. Aerate the Pond: Even in winter, oxygen is crucial. Aeration systems or air stones can help prevent the surface from freezing entirely, allowing for gas exchange which is vital for fish health.

Protecting Your Koi from Frost

  1. Install a Pond Heater or De-icer: These devices can keep a section of your pond ice-free, ensuring essential oxygenation.
  2. Avoid Breaking Ice: Never forcefully break the ice on a pond's surface, as the shock waves can stress or even harm the fish. Instead, use a hot pan to melt a hole if necessary.


Pond Depth Matters

A deeper pond can offer a sanctuary for koi in winter. The bottom of the pond is the warmest, and koi tend to hibernate there. If your pond is at least 1.5 metres deep, it can provide a stable environment, even in the harshest winter.


Regular Health Checks

Even in winter, regularly inspect your koi for signs of distress or disease. Look for clamped fins, sores, or unusual swimming patterns. Catching potential problems early can be the key to ensuring the health and longevity of your koi.


Winter can be a testing time for koi keepers, but with the right knowledge and preparation, it's possible to provide a safe and healthy environment for your fish. As spring approaches and temperatures begin to rise, you'll find your koi emerging vibrant and ready for the warmer months ahead.