How Do I Know if My Koi is Stressed

How Do I Know if My Koi is Stressed


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As a caregiver to Koi fishes sometimes your Koi exhibit some odd behaviors that make you ask yourself “how do I know if my koi are stressed?” Fish dislike changes in their environment, especially temperature. Any changes put the fish under more stress, and the bigger and quicker the adjustments, the more stressed they become.

The most important thing to note when your koi are showing signs of being stressed is to determine what exactly in your care is stressing them out. Is it something you are doing? Is there a change that needs to be made?


Do Koi Get Stressed?

Yes, koi fish get stressed just like any other living creature in the world. Stressful situations that put stress on Koi are usually sudden environmental changes, overcrowding, or unnatural competition for resources.


Stress is an unavoidable part of life for any living creature. It’s simply a reaction to something uncomfortable and new. For fish, it’s important to be able to remain in homeostasis, the ideal state for every organism. This means their environment is stable and unchanging, but when things are different they have to adapt to it.

Fish have evolved to react to stressful situations with fight or flight. If faced with an immediate threat fish can rapidly change color, moving faster and breathing more frequently. Koi stressed by a lack of oxygen will gulp air from the surface, and if stressed by being chased by another fish they will often dart backward.


What Causes Koi Fish To Be Stressed

There are several reasons why a Koi fish may be stressed but some of the most common reasons are:

  1. Not Enough Room: If the aquarium or pond is too small for them to exercise out and swim freely your koi fish will eventually get stressed out because they need more room than you had provided for them.
  2. Not Enough Food: If there is not enough Koi food to give your fish they may start showing signs of being stressed.
  3. Poor Water Quality: Koi fish can also get stressed because of poor water quality. It’s important to always check your filtration system and make sure everything is working properly. The condition of the pond should be checked frequently so any changes in Koi’s behavior can be noticed and fixed before the problem gets out of hand.
  4. Parasites: Diseases can be a cause of stressed out koi fish. Parasites will make the Koi feel uncomfortable and stressed because it’s trying to take over their bodies.
  5. Injuries from Other Fish: Is another fish nipping at your koi? This can stress out your Koi which puts them in jeopardy of becoming ill.
  6. Improper Water Temperature: If your Koi fish’s water is too cold they will be stressed out and if the water temperature is too hot it can stress them out too. It’s important to keep an eye on your koi fish so they are comfortable at all times.
  7. Overcrowding: Overcrowding your koi pond or aquarium with fish can increase stress levels amongst Koi fishes. If there is not enough room for all the koi to swim around and play they will always be stressed out about it.
  8. Pollution: Overly use of insect spray, spills, and other forms of chemicals can cause pollution in your pond, which can lead to a stressed out koi.
  9. Aggressive Tank Mates: Placing a Koi with fishes that are too aggressive or too large with other small fishes can put the lives of the smaller fish in danger and make them stressed because of the threat the bigger fish pose to them.
  10. Sound: Loud noises, such as a heavy rainstorm or a lawnmower can easily stress out your koi especially if it’s an overly loud sound they are not used to.

How Do I Know if My Koi is Stressed?

There are usually some telltale signs of stressed koi an experienced caregiver can sense and as time goes by it becomes easier to know if your Koi is stressed out by simply observing their behavior. If you notice any of the following symptoms then it’s time to take action because stressed-out koi fish are prone to disease or death.

Below are 14 common signs to know if your koi are stressed: 

  1. Crawling on the sides of tank or pond
  2. Over-eating and under-eating
  3. Loss of coloration(in stressed koi this can mean anything from very slight to outright white)
  4. Listlessness
  5. Spinning
  6. Rapid breathing
  7. Clamped fins
  8. Not eating or has stopped eating
  9. Scratching against the bottom or sides of the aquarium or pond
  10. Hanging at the bottom of the aquarium or pond
  11. Hiding behavior,
  12. Tail biting (even in beta fish),
  13. Gasping at the surface of the water.
  14. Laying on its side and not swimming upright like it normally does.

How Do You Calm A Stressed Koi Fish?

Aside from ensuring your koi pond is clean and aerated if you want to stop koi fish from stressing you also need to make sure the environment of your koi aquarium or pond is stable. Stability in this case means preventing any sudden changes that will upset or stress out your fish.


To calm and destress a koi fish you can try the following 5 suggestions:


1) Introduce More Hiding Place

Add more hiding places for stressed out koi. More hiding spaces mean less stress for your stressed-out Koi fish. You can use plastic plants or you can stack rocks together to make an area where stressed-out koi will feel safe and secure. Be sure to stack enough rocks so that your stressed koi can rest comfortably.

2) Put A Mirror In Your Tank

Put a mirror inside your stressed koi’s tank or pond because stressed out fish are always looking for other stressed koi to make them feel more at ease around other stressed-out fish. Be sure to only use the mirror only when you have time to monitor your stressed koi though because stressed out fish may become even more stressed if it is constantly stressed out about other stressed koi looking at them.


3) Excercise Your Stressed Koi

Exercise your stressed koi by doing some water aerobics with stressed out fish to help them burn off stress and ease its mind a bit. You can place a couple of inflatable beach balls or rubber rings inside the aquarium or pond for stressed out Koi to play with.

4) Offer Your Koi Varieties of Food

Offer stressed koi a variety of foods to eat. Koi stressed out about not having enough food will become stressed out if they don’t have a good selection of different types of stressed koi food to choose from. Although it is best not to feed stressed out fish too much, you should still make sure your stressed koi has its favorite foods to eat.

5) Reduce Water Current

Provide stressed koi with a gentle water current to help stressed out fish ease their mind and feel less stressed out. You can create a gentle water current with a battery-operated device or you can attach stressed koi hose to an air pump. The key is not to have stressed out fish stressed about being stressed out so make sure the stressed koi current is gentle and non-stressful.



You now know how to tell if stressed out koi are stressed, and hopefully, you can better calm your koi fish stress with some of these suggestions. Koi fish are too wonderful to be stressed out all the time so try your best to keep stressed-out fish calm and at ease. Stress is a killer for koi fish, and you should do all you can to keep your stressed koi happy and stress-free.

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