Keeping koi ponds is becoming increasingly popular and as more and more people start to keep koi fish, the numbers of questions that we see each month about keeping koi also increase.
We have noticed a wide range of different questions being asked from koi keepers each month over the last year or so but in recent months, there has been a spike in people having problems with their koi fish not eating.
Due to this being a serious issue that is often easy to fix in many cases, we wanted to publish our own article going over the more common causes of a koi not eating as well as how you are able to fix them.
Ideally, you will also be seeking advice from a veterinarian too as some of the potential problems that we will be covering below as serious and may require professional treatment!
How Long Can Koi Stay Without Food?
Koi fish are able to fast for long periods of time and can often go for around 2 weeks without eating before they start to experience any ill effects.
Koi have evolved to be able to do this as in their natural environment, there are often times when food is scarce so they have had to adapt.
During this time, a healthy koi should be able to live from fat stores as well as any fod that it is able to forage from its pond.
Please note that just because a koi can technically live for two weeks without food does not mean that this should be the norm for the fish and the longer it goes without food, even within this two week period, the more risk there are to the fish.
Why Is My Koi Fish Not Eating?
There are a number of common reasons that your koi fish may not be eating with some being easy to fix where as others being serious and difficult to fix in most situations.
We will be going over an overview of each of the common reasons that your koi fish may not eat below but there are some less common reasons that are very rare.
You Are Using An Unsuitable Food!
One of the most common reasons that koi fish do not eat is simply because they are being offered the wrong food for their needs.
This is particularly common in new koi keepers who do not realise just how many different koi foods are available on the market and assume that all koi foods are the same.
In reality, koi foods are often very different and koi can be very fussy eaters, much like humans!
The vast majority of koi keepers will feed their koi a high quality koi pellet food as they are nutritionally complete, easy to store and generally quite cheap too.
When choosing koi food pellets, you need to ensure that you are picking a food that is complete and nutritionally balanced for koi as well as being suitable for the time of year.
For example, koi foods that are high in protein are often better suited to spring and summer when koi are growing and need more energy whereas koi foods that contain less protein and more fibre are often better suited to autumn and winter when koi are slower and do not need as much energy.
Problems With Temperature!
In the wild, koi will often stop eating when the water temperatures start to drop as they know that they won’t be able to digest their food properly in the colder water.
As koi are cold-blooded animals, their metabolism slows right down in cooler water which means that they can’t digest their food as quickly or effectively.
This is why koi often slow their eating pace in autumn and winter as the water temperatures start to drop as they know that they won’t be able to digest their food.
If your koi fish are not eating, one of the first things that you should check is the water temperature as if it is too cold, they may simply not be able to eat.
In most cases, koi will slow their eating when the water temperatures fall below 50 degrees Fahrenheit but this can vary slightly from fish to fish.
Are You Running A Closed Ecosystem Pond?
A closed ecosystem pond is usually designed to be as close to being self sufficient as possible for the needs of everything living in the pond.
This is an advanced setup and is usually not beginner friendly as you do need experience to be able to successfully plan out a closed eco system pond.
Most closed ecosystem ponds will have multiple sources of natural food in them that are based around what koi fish will naturally eat in the wild.
This can result in your koi not eating the pellets that you will usually feed them at certain times of the year due to there being plenty of live food in their pond with this being totally normal and natural for this type of setup.
Issues With Water Quality!
Another common reason that koi fish may stop eating is due to problems with the water quality in their pond.
Koi are very sensitive to changes in water quality and even a small change can often result in koi becoming stressed which will usually cause them to stop eating.
If your koi fish have stopped eating, it is always worth checking the water quality in your pond to see if there are any obvious issues.
You can check the water quality yourself using a simple test kit or you could also take a sample of your pond water to your local fish store or koi dealer to have it professionally tested.
If you do find that there are issues with the water quality, it is important to address these as soon as possible as koi can become very ill if they are kept in poor water conditions for too long.
Stress And Anxiety!
Koi are very sensitive creatures and even small changes in their environment can often cause them to become stressed.
If koi are stressed, they will often stop eating as they do not feel safe or secure enough to eat.
There are many different things that can cause koi to become stressed such as overcrowding, poor water quality, predators and even just a change in their routine.
If your koi fish have stopped eating, it is always worth trying to identify any possible sources of stress or anxiety in their environment.
Once you have identified the source of the stress, you can then take steps to try and reduce it which should help to encourage your koi to start eating again.
Disease Or Illness!
Another possible reason for koi fish not eating is due to them being ill or suffering from a disease.
There are many different diseases and illnesses that koi can suffer from and some of these can cause koi to stop eating.
If you think that your koi may be ill, it is important to take them to a koi dealer or vet as soon as possible so that they can be properly diagnosed and treated.
A koi dealer or koi vet will usually be able to tell if koi are ill just by looking at them and they will also be able to carry out any necessary tests to confirm their diagnosis.
Problems With Water Hardness!
Another reason that some koi fish may stop eating is due to problems with the hardness of their pond water.
The water hardness of your koi pound should always be around 9-18 degrees dH.
Anything outside of this can cause your koi to slow their eating paces and in extreme cases, not eat at all.
Koi fish can often suffer from internal parasites which can make them very ill and in some cases, cause them to stop eating altogether.
Due to the semi-wild nature of a koi pond when compared to other species of fish that are kept in an aquarium, you may commonly have problems with parasites in your koi requiring regular treatments to manage the issue.
If you think that your koi may have internal parasites, it is important to take them to a koi dealer or koi vet as soon as possible so that they can be properly diagnosed and treated.
Issues With O2 And CO2 In The Pond?
Another common reason that koi fish may stop eating is due to problems with the levels of oxygen and carbon dioxide in their pond.
Koi require a high level of dissolved oxygen in their water in order to breathe and if the levels of oxygen are too low, koi will often stop eating as they become stressed.
You can check the levels of oxygen in your koi pond using a simple test kit and if the levels are low, you will need to take steps to increase them.
One way to do this is to add an air pump to your koi pond which will help to increase the level of dissolved oxygen in the water.
You should also make sure that there is plenty of surface area in your koi pond for oxygen to be able to dissolve into the water.
Another way to increase the levels of dissolved oxygen in your koi pond is to add plants as they will help to produce oxygen through photosynthesis.
If the levels of carbon dioxide in your koi pond are too high, it can also cause koi to stop eating.
Carbon dioxide is produced by koi as they breathe and if the levels become too high, it can cause koi to become stressed and stop eating.
You can check the levels of carbon dioxide in your koi pond using a simple test kit and if the levels are high, you will need to take steps to decrease them.
One way to do this is to add an air stone to your koi pond which will help to release some of the carbon dioxide that has built up in the water.
Ammonia And Nitrate Levels Are High!
Another common reason for koi fish not eating is due to high levels of ammonia or nitrates in their pond.
Ammonia and nitrates are both waste products that are produced by koi and if the levels become too high, it can cause koi to become ill and stop eating.
You can check the levels of ammonia and nitrates in your koi pond using a simple test kit and if the levels are high, you will need to take steps to decrease them.
One way to do this is to carry out a water change and remove some of the water that contains high levels of ammonia or nitrates.
You should also make sure that you are regularly cleaning your koi pond and removing any waste that has accumulated.
Your koi pond should also have a good filtration system in place to help remove ammonia and nitrates from the water.
Another common reason for koi fish not eating is due to constipation.
Constipation is a common problem in koi and can be caused by a number of different factors such as a lack of fibre in their diet or dehydration.
If your koi are constipated, it is important to take them to a koi dealer or koi vet as soon as possible so that they can be properly diagnosed and treated.
Your koi may need to be given a course of medication to help relieve their constipation and you may also need to make changes to their diet.
There are a number of reasons why koi fish may stop eating, including problems with parasites, levels of oxygen and carbon dioxide in the pond, high levels of ammonia or nitrates, and constipation. If you think that your koi may be experiencing any of these problems, it is important to take them to a koi dealer or koi vet as soon as possible so that they can be properly diagnosed and treated.