Why Your Koi is Not Eating and 4 Things You Can Do About It

Koi are a beautiful fish that you can be proud to show off to friends and family. Indeed, they are family themselves. Some of them get trusting enough to even eat out of your hand. It is a joy to have these water critters.

As a koi owner, you might have concern for some of their traits though. Such as when they stop eating as much as you think that they should be. In many cases, this is no reason for concern as I will go into in this article.

How do you know when your koi is not eating if it is a cause for concern? Don’t worry. This article will answer your questions to find out if your koi not eating is a reason to worry or not. I’ll also give advice on what to do when there is possibly a problem.

Typically, if it’s cold outside koi won’t eat anything because their metabolism shuts down completely. They just can’t digest food. Also, poor water quality and sudden environmental changes can also be contributors to your koi’s changing eating habits. Illness can also affect their appetite.

Below I will talk about a number of reasons that may affect a koi’s appetite. You will learn why it is that certain circumstances can cause koi to stop eating the food you throw out to them. I will give you some tips on how to solve the problem too.

The metabolism of koi

Many things can affect a koi carps ability to ingest food. The first thing to know about is their metabolism. Koi don’t have a stomach. They can’t eat a lot at once and store the food in their stomach for digestion as people do. 

Instead, koi eat small amounts of food in frequent fashion. Since they don’t have the stomach we have they feel full very fast. Because of this, they are hungry all of the time. They need to be fed small amounts at frequent intervals.

Koi are cold-blooded

Temperature plays a major role in helping the Koi to digest food as well because they are cold-blooded. The colder it gets, the slower your Koi’s metabolism gets. Heat speeds their metabolism up and coldness slows it down.

 This is why in the summer Koi are always hungry and during Winters temperature lows the Koi’s ability to digest is hampered, therefore they will eat a lot less if anything at all.

Water Quality Problems

Bad water quality can wreak havoc in your koi pond habitat. For example, it can make koi lose interest in their food eventually. Koi are very sensitive fish, with abrupt spikes or drops being very stressful and dangerous to your koi’s health. 

Since it’s difficult to determine if water quality is the actual problem visually, the best way to investigate is to use a pond water tester kit which gives out results for a few different ranges of measurements. 

When testing water you need to pay close attention to readings for ammonia levels, nitrites, pH and KH, as these are the most common problems that affect appetite.

When you need not worry about your koi not eating

Koi can’t digest food like we can because they don’t have a stomach. Being cold-blooded, their metabolic rate shifts with the change in outer temperatures. In the coldest parts of the Winter months don’t be surprised if you don’t need to feed your koi hardly at all. Koi stop eating altogether around the Fall and Winter.

When should you worry?

If your koi don’t want to eat whenever it is warm and sunny out, then you might want to start being concerned. In the summer koi are supposed to be wanting food and them not eating could be a serious problem. Problems could be:

  • Illness
  • Boredom with their food
  • Changes in the water quality

If your koi isn’t feeling good, then they will probably go off somewhere alone to recover. They won’t be too interested in feeding at this time until they get to feeling better. If they get sick for a day and get right back to eating it probably isn’t anything to be worried about. Them not eating for days may be a reason for concern, however.

Koi can get bored with their food. Their taste buds have their likes and dislikes just like how everyone hates celery(that’s not just me, right?) Actually koi might like it!

 They might get tired of their diet if it’s that cheap stuff with too much filler and void of nutritional good stuff. Splurge on the more expensive but higher quality food.

Changes in the ponds acidity level can also affect your koi fishes health by making them not feel very good. Fish waste, pollutants, algae overgrowth, and other toxic substances in the water may be making your fish sick.

What to do about your koi not eating?

Here’s your to-do list in dealing with koi not eating. These 4 tips will help you get your fish chowing down in no time.

1)Just know that in the Winter it’s alright if your koi aren’t eating.

New koi-keepers might find it odd when one day their fish are eating like an all-you-can-eat buffet, but then temperatures drop and all-of-a-sudden they just stop eating. This is topor, or hibernation, time. 

In Autumn they will possibly slow their consumption quite a bit and when water gets down to 50 degrees then they will stop eating altogether. This is normal, but still concerns newbies to koi ownership. Even though they are in hibernation at the time there are things you can do to keep them cozy such as:

  • Keeping a circle cut out in the ice with a de-icer. This will make sure gases don’t build up and suffocate your koi
  • Continuing to pump oxygen into the water with a pond pump
  • Putting in a fish shelter to give them a place to snuggle down in
  • Parasite control in Autumn leading up to Winter

2)Give your water a check-up.

Another thing to check if your koi isn’t eating regularly is your water quality. The most important things to check for are the pH, KH, and aeration. The only way to check some of these is with a pond water tester kit.

3)Get a better koi food 

You would get tired of eating the same thing over and over again, wouldn’t you? It’s not any different with koi. Maybe it’s time to upgrade your koi’s food. Good protein-rich food would be a great change so I would recommend a product like Hikari Gold on Amazon.

4)Get rid of the pests(parasites) or treat infections

Is your koi sick? Is it ill? In cases like this, it is time to put a product in your pond that will take care of infections and eliminate parasites. A good product for this is called Aquarium Pharmaceuticals Melafix Fish Remedy which would be great to add in the fall right before the freezing temperatures start.

I hope these tips help you get some nutritional good stuff in your koi’s bellies. Follow these tips to get your pet fish eating and don’t forget to like or follow me on my social channels below. Leave me a reply if you have any questions. 

Image by Clker-Free-Vector-Images from Pixabay

6 thoughts on “Why Your Koi is Not Eating and 4 Things You Can Do About It”

  1. Thank you for this great and in depth post, thou I do admire koi very much and always cherish them at sight but I have no personal knowledge of their metabolism, now I know the fact that they are cold blooded and have no true stomach hence the reason for their small food intake is duely justified. 

    • Hello Charles

      Koi do have small guts and I have learned that you don’t want to give them any more food than they can eat in 5 minutes. I could lose a lot of weight if I ate for only 5 minutes. Do you think this eating could be the next crash diet trend? Are we about to be rich?

      In all seriousness-Thanks for reading and glad you’re learning about koi


  2. Great article. I suspected water quality would have an impact on Koi’s appetite as it does with most fish though I didn’t know about the water temperature. Thanks for clearing this up. 

    You suggested a fish shelter to help them snuggle down in. What is this and how does it work? Do you make them or buy them? If they are cold blooded will they warm themselves up when snuggling. Which raises the next question can Koi spoon?

    • You can buy them a shelter and maybe, just maybe, they’ll spoon. I don’t know the answer to your last question. What happens in the shelter stays in the shelter. Let me know if you find out.


  3. I just added a few baby kois into our newly designed pond. We have been briefed by the seller on some basic care, but your article sheds new light on certain things that I don’t know as a new owner. We live in the tropics so under this condition, do they even hibernate? If they do, at what age do they start? I mean these are babies and if they stop eating, I would be concerned with the growth rate. Thanks for your input in advance.

    • Hi Cathy, thanks for visiting. I couldn’t see koi hibernating in such warm weather. Instead I would be more concerned with keeping the algae controlled. Your fish will probably stay hungry frequently unless the water quality is affecting their appetites or feeling under the weather.


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