Why are my Koi pond fish not eating?

If your pond fish have stopped eating this could be something as simple as the current climate (too cold), it could also be related to the food (stale) or you're simply overfeeding your fish.

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What factors can cause your pond fish not to eat?

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If your pond fish have stopped eating this could be something as simple as the current climate.  During colder temperatures, fish generally stay at the bottom of your pond and consume less food.  With warmer weather, fish will either feed like crazy, or will just surf the top of the pond completely uninterested in food.

I understand the concern that comes when koi pond fish refuse to eat. There could be several reasons behind this behavior, and I will explore these factors to help you address the issue.

Water Temperature

Koi are cold-blooded creatures and their metabolism is highly dependent on water temperature. When the water temperature drops, their metabolism slows down, and they require less food. This is most common during autumn and winter months. To ensure your pond is prepared for these seasonal changes, check out our free 4-part guide on autumn pond preparations.

Poor Water Quality

Poor water quality can be detrimental to your fish's health, and it may cause them to lose their appetite. Factors such as high ammonia or nitrite levels, low oxygen, and dirty water can all contribute to poor water quality. To maintain a healthy pond environment, consider using the right pond pump and implementing proper filtration techniques. Additionally, learn how to save on pond running costs while maintaining a clean and healthy environment for your fish.


If your koi are not eating, they may be unwell. Observe their behavior and physical appearance to identify any signs of illness. Some common signs include lethargy, swimming upside down, or spending excessive time near the surface gasping for air. To learn how to address specific health issues, visit our help section.


Stressful conditions can make your koi lose their appetite. Factors such as overcrowding, aggressive tank mates, and sudden changes in water parameters can cause stress. Ensure your pond has adequate space for your fish and that their environment remains stable.

Inadequate or Inappropriate Food

Koi may refuse to eat if the food offered is of low quality or not suited to their nutritional needs. Ensure you're providing your fish with the right type of food and follow proper feeding guidelines.

Weather Changes

Fish may also alter their eating habits due to changes in weather conditions, such as thunderstorms or heavy rain. Monitor weather conditions and adjust feeding accordingly.

Other Factors

There may be other factors causing your koi to lose their appetite. For example, if you have recently introduced new fish to the pond, they may require some time to adjust to their new environment. Additionally, ensure your pond is free from predators and pests, such as rats or mosquitoes.

To summarize, several factors can contribute to your koi's reluctance to eat. By addressing these issues and maintaining a healthy pond environment, you can ensure your fish remain happy and well-fed.