Quarantining New Koi


Congratulations on your new koi purchase! I’m sure that you are thrilled with your new acquisition. You’re rushing home to release your new koi into the pond so you can begin enjoying its beauty, smile as it learns to come quickly to the surface when it hears your footsteps approaching, train it to eat from your hand, adore its scales glistening in the sunlight, and watch it swim leisurely amongst your existing koi collection. Sigh. Ah, life is good. 

 WHOA! Let’s take a deep breath and think about what you are doing. Listen to that little voice in the back of your mind that’s whispering, “Quarantine….. Quarantine.”  But this new beauty looks perfectly healthy. It seems perfectly healthy. I think it’s perfectly healthy, right?

That is a big assumption which may cause heart-break in the near future especially if you don’t listen to the voice in your head that is now screaming, “QUARANTINE…..QUARANTINE!!!”  

So, why quarantine koi fish before introducing them into our beloved koi collections?

First, the quarantine process gives the newly acquired koi time to rest and recover from the stress of handling, moving and transport. The journey to its new home may have stressed the fish immensely, which can weaken its immune system. Unfortunately, you can’t really know how the fish was handled nor the water quality conditions it was subjected to prior to coming into your care. Remember that a koi with a weakened immune system is highly prone to disease and parasite attack. Quarantining new koi fish gives them time to bounce back and get back into tip-top health. And, healthy koi have a much easier time fending off parasites and bacterial infections without human intervention.

Secondly, the koi quarantine period allows the new fish to become accustomed to the water parameters of its new home and to the pathogens living there. Your new pet, being a koi fish, has already been exposed to pathogenic bacteria, because pathogenic bacteria are in every body of water that contains fish. The question isn’t IF the koi has been exposed to pathogenic bacteria, more importantly how high or how low the level of the pathogenic bacteria has been. 

Lastly, another reason for quarantining new koi is its current susceptibility to disease and parasite attack, you don’t want to expose your entire collection to the issue should there be an outbreak of some sort. The segregation of all new arrivals will provide ample time for any pathogens and parasites to cycle and become apparent. In the unfortunate event that this new fish becomes ill with disease or parasites it will be much easier to deal with the situation in the contained space of a quarantine tank rather than in your entire koi pond. 

The idea of a koi quarantine tank system is to provide a safe and secure place with optimum water quality to allow the new koi time to relax and recover from the ordeal of transportation to its new home; all the while providing an opportunity for the owner to keep a close eye on the fish and monitor its health before introducing the newcomer to the other pond inhabitants. 

Quarantining new koi fish is a big commitment, and certainly not a simple task. If not conducted properly then you may be compounding stressors on the new fish and actually do more harm than good.  You have spent hard-earned money on your koi pond and live fish, quarantine could be considered insurance for your investment. With any new fish purchase a quarantine period is highly recommended. However, if you do not have the time or patience to set up an adequate quarantine system, or don’t follow good quarantine procedures, then you might be better off releasing the new fish directly into your pond and hoping for the 


5 Components Required For a Good Koi Quarantine Tank System

Quarantining new koi can be simple if you have the right equipment for the job. Here’s a list of the 5 most important components of a good quarantine tank system.

  1. The Quarantine Tank - Use only plastic, rubber or PVC products. Galvanized tanks can be harmful to fish. Use a tank of sufficient size to hold the fish comfortably. A 100 gallon tank can quarantine 4 koi of 10” size. Heavy-duty collapsible quarantine tanks can be purchased online.

  2. Tank Heater - A submersible 300 watt heater should do the job. Maintain a water temperature in the 74°-78° F range throughout the quarantine period.

  3. Bio Filtration with Pump - Every quarantine system will need a bio filter and circulating water pump. The pump should be large enough to circulate the entire volume of the tank every 30-45 minutes. The bio filter can be a little tedious to get going; an adequate bio filter can take up to 3 weeks to become aged. To jump-start the process you can place some extra sponge type filter media your koi pond’s filter for several weeks. Then transplant the sponges now seeded with good bacteria into the quarantine system filter approximately two days prior to introducing new koi to the quarantine tank. Be sure to use de-chlorinator before installing the pre-seeded filter media as any chlorine in the water will kill off the bacteria and undermine your efforts.

  4. Aeration Device - All fish need oxygen and so does the bio filter. Keep your aeration pump running with at least one air stone on the bottom of the tank at all times. Any span without aeration is asking for trouble. 

  5. A Lid or Cover - Koi will jump in attempts to flee unfamiliar surroundings. You should have a weighted net large enough to cover the entire tank. Many koi have been lost by jumping through the smallest area left uncovered and unattended. Another option is to build a sturdy wooden frame and staple plastic mesh onto the frame. You should not use clear plastic or glass as a cover for quarantine tanks because they will increase the temperature of the water. Your cover should allow for fresh air yet protect your koi from predators.

Should I put a goldfish in my homemade koi quarantine tank?

It is true that koi are very social and don’t do well if isolated by themselves. But, do not run to the local pet store and buy a ‘sacrificial’ goldfish, as a quarantine tank companion, or in an effort to start the nitrogen cycle. You may be getting more than you bargained for, as the goldfish can be the start of many unintended consequences. If a situation arises how will you know if it is due to the new koi or the inexpensive goldfish?  Instead, it is recommended that a fish from your current stock be placed into the quarantine tank with the new arrival as a companion, and that fish may very well be a goldfish. The addition of any small fish from your koi pond will introduce the newbie to whatever is in your pond, and vice versa. If you only want to get the nitrogen cycle started then add a small handful of feed pellets to the tank every other day. As the feed dissolves ammonia will be produced, be circulated by the pump and feed the good bacteria in the filter, thus starting the nitrogen cycle. 

How do I seed a biological filter on the koi quarantine tank?

Koi pond filters and koi quarantine tank filters can take several weeks before they become colonized with good bacteria: aerobic bacterium Nitrobacter and Nitrosomonas. These bacteria are required to consume ammonia that is produced by the fish, reduce it to nitrite, and then to harmless nitrate.  One way to jump-start your quarantine tank filter is to use some filter media from your active koi pond’s filter system. By transferring some of the filter media from your existing koi pond you will be planting seeded media into the temporary quarantine filter. This media should already be laden with live bacteria that will be needed to control ammonia in the quarantine tank water. But, it is never a good idea to return the bio media that was used in a quarantine tank back into the pond filtration system. Alternatively, there are several good bacteria products on the market for seeding bio filters.

How long do I quarantine new koi fish?

How long to quarantine new koi is up to the owner, although 4-6 weeks is common.  

What about water changes during quarantine?

Water changes are very important during the quarantine period. You need to exchange 10-15% of the total water volume twice weekly when a good bio-filter is actively working. If you do not have a bio-filter established then your quarantine tank will require a 50% water change daily. You should test the water for ammonia and nitrite daily. Both should be maintained in the range of zero-.01 ppm. And always keep plenty of chlorine remover products on hand and use accordingly with every water change.

Where should I set up the koi quarantine tank?

Spend some time to determine the ideal location for your quarantine tank. Put the quarantine tank where you will have easy access to it and preferably where it will not get too hot, or too cold. It should have access to electricity, your water source, and shade for part of every day. If it will be in your garage then use the sniff test. Close your eyes and sniff, if you can smell gasoline or paint fumes so will your fish! The aeration pump will transfer them into the water. Either store gas powered equipment, gas, oil and paint products elsewhere, or find a better location for the quarantine tank. Motor vehicle exhaust should also be considered.

How about feeding koi in a quarantine tank?

Feeding koi in the quarantine system gets very tricky. Generally, koi can go without food for two weeks, but it seems cruel to make them fast for an extended time. Over feeding in the quarantine system can bring on big troubles because bio filtration is slow to get going or very likely inadequate in most cases. High ammonia is a serious threat to your fish while under quarantine. Do not feed fish in the quarantine tank for the first two days. Then, begin by offering very small portions of food once per day. Be sure to monitor ammonia level with a test kit and stop feeding and perform a water change if the ammonia begins to creep up.

What treatments do I use on koi during quarantine?

It is best not to use any type of treatment in quarantine unless you know what and why the treatment is being administered. Salt is probably the safest and most effective additive for use in the koi quarantine tank. Salt will kill or slow down most parasites and ease the stress level for your koi. Salt concentration should be maintained at .3 ppt, or 3 lbs. per 100 gallons of water. For therapeutic application it is recommended to use only non-iodized salt. Remember to add salt with every water change.

Information from KoiHealth http://www.koihealth.info/quarantining-koi.html