Do you need to quarantine Koi?

To quarantine or not to quarantine, that is the question… The word ‘quarantine’ (which, incidentally, comes from the Latin quarantine, meaning ‘forty days’), is a length of time in which a disease can be incubated, and therefore expressed in an organism. That way, it’s possible to see who does, and doesn’t, carry a specific disease. Traditionally, forty days is the time that many major diseases will incubate in humans, but the situation for fish is a little different, and our view of what quarantine means for them is something of a ‘grey area’.

Wherever you source your Koi from always quarantine them before introducing them to your pond. It’s a question of “best practice” and however much you trust the honesty of your supplier, and however good they say their bio-security is, it is your personal responsibility to ensure the welfare of your existing population of fish, not theirs, and if they make a mistake and compromise their bio-security, by quarantining any new Koi you can help to make sure it isn’t you that pays for that mistake.  Fish suffer from diseases just like any other animal – it’s part of nature that they do and you can’t get away from it. Of course, you can do a lot to ensure that they stay healthy but, just occasionally, they are bound to fall victim to some kind of parasite, viral or bacterial problem.  You can reduce the risk of them being exposed to any of these problems in the first place by quarantining any new additions to your pond.  The stress of moving to a new home can lead to a reduction in the effectiveness of a Koi’s immune system and during this vulnerable time, any number of common diseases can take advantage of that and trigger a health problem for your new Koi.  For this reason, a tank which is completely separate from your main pond, with its own filtration, bowl and net and ideally with the ability to be heated, will provide an environment that allows you to monitor your new Koi closely and respond to any problems that may arise.  Six weeks is a minimum period for quarantining Koi and should provide enough time for any underlying bacterial or parasite problems to become apparent.  During that time it is also recommended that the Koi be heat cycled in order to try and find out if your new Koi may have been exposed to, and might therefore be carriers of, Koi Herpes Virus (KHV).  KHV, which is deadly to most Koi and which can remain dormant in any surviving Koi, is active at between 18 and 27 degrees Centigrade and Koi should be taken from a temperature lower than 18 degrees to, for example, 23 degrees and held at that temperature for two weeks – that’s how long it can take a Koi exposed to the virus to show symptoms.  After that time the cycle should be repeated if possible.  This heat ramping is not absolutely guaranteed to bring out the virus but it is the best method yet discovered of doing so. Once your Koi have successfully completed their quarantine period, they can be introduced to your pond with the confidence that you have done everything possible to ensure the health of all your Koi.

Mark Davis 07/09

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