Why Is My Koi Staying In One Spot & Not Moving? (Solutions)

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Why Is My Koi Staying In One Spot and Not Moving? (Reasons & Solutions)

A koi which doesn’t move or remains on the pond bottom could be due to a number of factors, including stress, age or parasites. Kamillo Kluth / CC BY 2.0

When they’re accustomed to their environment and are generally happy with ambient conditions, koi are energetic fish that explore most areas of a pond. They swim to and fro, eager to interact with one another and seize the day! In ponds with an optimal depth, they can easily navigate through the full water column. They normally feed at the surface and may take occasional dips to the deeper parts of a pond. However, they will seldom stay on the bottom or in one spot for more than a few minutes.

Healthy koi move with alertness and speed, especially when a person is around to view them. If you find one that isn’t moving or is displaying erratic swimming behavior, particularly during the spring and summer months, you may need to take action. Immobility even during feeding time is definitely a cause for alarm, as only serious issues may stop a koi from excitedly taking food. Loss of buoyancy control, sideways swimming, or upside-down koi are also distinct signs that something is wrong.

Once you spot a koi displaying odd symptoms, you must first check if it is still breathing. Chances are it’s still alive, but will need immediate care or medication to recover. A principal cause of koi immobility is stress, which can be caused by multiple factors. Below is an outline of potential causes of koi not moving, some of which are difficult to detect. Many of these are natural or can be fixed without professional help, but others may require an expert’s opinion and guidance.

Causes of Koi Staying in One Spot

1) Poor water quality

Poor water quality, including excess nutrients, ammonia, or a fluctuating pH, can cause koi to become sluggish and immobile.

One of the leading causes of koi immobility is poor water quality. High concentrations of nutrients can stimulate pathogenic growth in your pond and reduce oxygen levels. This can be indicated by strange behavior from multiple koi, although there will always be one or two to first show signs of ill health. Fish with compromised immunity are rarely able to survive through bouts of poor water conditions and will likely need special treatment or medication.

Once you spot a weak fish, check your water parameters as soon as possible. Make sure that your pond’s ammonia (NH3), nitrite (NO2), chlorine, and pH levels are within the normal range. Anything above zero for both ammonia and nitrite concentrations can indicate that something is off-balance or your filter is faulty. Fish that are subject to ammonia poisoning may choose to isolate themselves at the pond bottom. Peer closely at the fins and most delicate parts of these fish, as they may begin to display streaks of blood or erosion.

Your pond’s pH level should be between 7.0 and 8.0. Prolonged exposure to pH levels above or below this range can result in health problems due to metal toxicity (heavy metals dissolve in acidic water), hypoxia, or alkalosis. These can all cause lethargy and immobility. Make sure to check for water hardness levels as well. The GH (general hardness) of your pond water should be higher than 10˚dH, and the KH (carbonate hardness) should be higher than 6˚dH.

If any parameters are outside the normal range, your pond may need a heavy water change. It may also need to be supplemented with biological filters, mineral additives, or pond plants.

2) Low oxygen levels

Dissolved oxygen testing kit
You can use a test kit, like this one pictured above, to test for dissolved oxygen levels in your koi pond. The ideal level is 6 ppm (6 mg/L) or above. Glen Bledsoe / CC BY 2.0

In a koi pond, dissolved oxygen (DO) levels should be maintained at 6 ppm (6 mg/L) or above. Anything below this value can cause koi hypoxia and increase levels of harmful nutrients. Over time, poor oxygenation can lead to dramatically worse water quality. When ignored, these eventually have a combined effect that can complicate diagnoses of koi diseases. Ensure that it does not reach this point by keeping an eye out for early symptoms of hypoxia. These include sluggish behavior, lack of appetite, congregations near a water source (such as an air stone), gasping for air at the water’s surface, and pale gills.

Extended exposure to DO levels below 6 ppm can compromise koi immunity by lowering rates of tissue repair. It can also stimulate the outbreak of bacteria and parasites that may severely reduce rates of fish growth and survival. It is essential to routinely measure your pond’s DO levels as they can fluctuate as a result of increased fish density, salinity, and water/ambient temperatures.

Use a reliable DO meter or test kit, and make sure to test for DO levels at the water column and not just at the surface of your pond. If you find that these values are always insufficient, you may need to invest in more mechanical aerators, add oxygenating aquatic plants, or reduce your fish density. If you make use of electric air pumps, do check these for wear and tear and have extra parts on hand to prevent drops in DO. Even short periods of oxygen deprivation can be extremely detrimental to koi.

3) Parasites & diseases

A scanning electron micrograph of a trichodinid ciliate
Many fish parasites, such as Trichodina (pictured), can be too small to be seen with the naked eye and can remain undetected as your koi grow weak. A.D.M. Dove, Attribution, via Wikimedia Commons

Like all other animals, koi that are ridden with parasites and diseases are less likely to have the energy to move around. Parasites usually lead to infections and disease (and vice versa). When affected fish stay put in one place, it is likely that their swimming organs have been compromised. Check for these early signs of parasitism to prevent irreversible damage:

  • cloudy skin as a result of mucus production
  • lethargy or listlessness resulting in immobility (commonly shown by fish sitting at the pond bottom)
  • redness of the skin and fins
  • pale gills
  • cloudy eyes
  • distress on the pond’s surface

These symptoms can be caused by a wide variety of diseases and parasites. You will likely have to fish out your affected koi and check their exposed body parts for physical signs of infection. A mucus or skin scrape sample may also be needed to diagnose the occurrence of microscopic microbes. Many fish parasites, such as Trichodina and Ichthyophthirius multifilis, may be too small to be seen with the naked eye and can remain undetected as your fish grow weak.  

Another disease that may cause your koi to stay on the bottom and struggle to move around a pond is swim bladder disorder. This can either be permanent or temporary and will require close observation. Cooked or frozen green peas are common remedies to the temporary form of this disorder and should work in a few hours by reducing the pressure on your fish’s bladder. The permanent form will likely require professional treatment and involve surgery.

4) Fright & tiredness

Floating plants underwater
After removing the source of fright, you should provide your koi with more shelter or safe hiding places to prevent injury, such as adding more herbaceous floating plants. Photo from PxHere

When frightened, koi tend to panic or frantically swim towards areas where they can hide. They can easily hurt themselves or other fish in the process. Depending on the severity of their injuries or on their state of stress, koi will need some time to recover and may require additional treatments. Significant stress after a moment of fright can result in flashing behavior or koi crashing towards the bottom or sides of your pond. This can cause them to grow extremely exhausted.

When the source of fright is removed, they may stay immobile along the bottom of your pond for some time, but they should soon go back to swimming normally. Provide your koi with more shelter or safe hiding places to prevent injury. This can come in the form of herbaceous floating plants or smooth-edged man-made shelters that can sit along the bottom of your pond.

Other causes of exhaustion are significant water change, relocation from one body of water to another, and mating/spawning. Acclimatizing to new conditions and recovering from high-energy activities may cause koi to grow extremely weary, especially if water parameters are not optimal. You can opt to treat your pond water with additives to remove heavy metals, ammonia, and chlorine to aid in recovery. This would be highly beneficial for fish that have to adapt to new water, especially when colonies of healthy pond bacteria are yet to become established.

5) Winter temperatures

A frozen koi pond
If your koi pond has frozen over, koi will gravitate towards the bottom part of the water column as it’s warmer there. Liz West / CC BY 2.0

Koi are poikilothermic fish that depend on water temperature to regulate many of their internal bodily functions. As temperatures drop during winter, koi metabolism slows down. This affects their energy stores and their swimming behavior.

If your pond has frozen over, your koi will gravitate towards the bottom part of the water column, where the temperature is considerably warmer. They may often appear to not be moving under the ice. If you observe them for longer periods of time, you’ll see that they make small movements and will swim over short distances. They must remain somewhat mobile so that their joints don’t seize up in the cold.

6) High fish density

Group of koi fish with open mouths
Overcrowding in a koi pond can lead to aggression and competition for food, creating stressful situations for your koi. Rob Chan / CC BY 2.0

An overcrowded fish pond can reinforce many stressful scenarios for your koi. A high fish density is associated with a higher waste load, increasing the demand for oxygen. Keep in mind that your koi will likely breed over time, increasing your fish density even further. Overcrowding can also lead to aggression and competition for food. Less vigorous koi may be deprived of fresh food and subjected to nutrient-poor or bacteria-ridden pond bottom scraps.

Moreover, the frequency of physical contact between fish may increase the chances of fright and disease transmission. Parasites will more quickly be transmitted from one fish to another, leading to an entire pond of sick fish! If that’s a nightmare for a pond owner, you can be sure it will feel even worse for the fish. Try to avoid overstocking your pond to save both yourself and your fish from having to deal with accumulated sources of stress.

7) Old age

Group of koi fish feeding in the water
When brand new or young koi are introduced to a pond, old koi may not be able to cope with the influx of new bacteria. Bernard Spragg. NZ / CC0 1.0

Old age can understandably cause koi to grow weak and tired, just as it affects all other living things. As organs begin to deteriorate, the immunity of your koi can grow stagnant or static.

Old fish are no longer able to tolerate and recover from water fluctuations as they once did. When brand new or young koi are introduced to a system, some of the older koi may experience ‘old pond syndrome’. This occurs when their bodies aren’t able to cope with an influx of new bacteria. Koi can supposedly live for dozens of years, but their lifespan is largely dependent on the skills of the pond keeper or on their genetic strain.

How to Respond to Immobile Koi

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Once you’ve spotted a koi that refuses to move and doesn’t readily take food, you must dedicate some time to evaluating your pond situation. Of course, you must first check if the immobile koi is breathing. You may have to gently fish your koi out of your pond if unable to get a good view of its gills. This will also allow you to inspect its capacity for movement, as a strong fish is more likely to swim away from a net. Check if any other fish are behaving similarly or showing signs of stress.

Go through your mental checklist of pond parameters, making sure to test for each one as accurately as possible. If you find abnormal levels of nutrients, pH, water hardness, or chlorine, respond by conducting a water change or by making use of pond additives to bring values back to normal. If your dissolved oxygen has suddenly dropped, consider adding an electrical air pump to your pond.

Do I Need to Quarantine My Sick Koi?

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If all water parameters are normal and your fish still show signs of stress, you will have to consider isolating the affected individuals.

Remove any dead or weak fish and transfer the live ones to a quarantine tank. This will help prevent transmission in case the affected fish have infectious diseases and parasites. For ease of mind, you may opt to consult a veterinarian or a more experienced pond keeper to help you determine the proper mode of treatment. If unable to do so, try to closely examine your koi for parasites. Make sure to inspect the mouth, fins, gills, scales, and tail of the fish for anything that appears out of the ordinary, but do so gently and carefully so that you do not cause injury.

If unable to detect any parasites, you can use a broad-spectrum antibacterial and anti-parasitic medicine made for ornamental fish. Make sure to read the label correctly and avoid simply eyeballing how much to add to your quarantine tank. It can understandably take some time for your fish to recover (if the ailment is reversible), so try to be consistent about maintaining optimal conditions for your sick fish. For good measure, give your quarantined koi additional time to recuperate separately even if they have begun to show signs of normal swimming behavior.

7 thoughts on “Why Is My Koi Staying In One Spot & Not Moving? (Solutions)”

  1. Brilliant information my fish are experiencing this problem hopefully I can save most I’ve lost three big koi so far it’s upsetting but thanks again for the info.
    Dave from bham.

  2. I have 7 juvenile Koi in approximately 400 gallons of pond. All were under 3″ when introduced to the pond 4 months ago and all but 1 are now over 6″ and quite active. The other, who was among the most active originally is still only 3″ and lethargic. Water tests good, thoughts?


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