Why quarantine Koi? I am frequently asked how important quarantine is and how high the risk of serious diseases such as Koi Herpesvirus usually termed KHV and Carp Edema Virus also known as sleeping sickness really are.  My work tells me that these diseases concern koi keepers very much and they need reassurance that dealers are putting newly imported koi through an appropriate form of quarantine. Diseases and how we limit their spread in koi is a multi layered subject and this article can only outline the current situation. Is quarantine important? Koi are challenged by the highly intensive system that produces them and distributes them around the world.  They are uprooted repeatedly interrupting their natural life cycles such as, growth, reproduction, and the development of the immune response.  This is often overlooked when looking for the cause of disease and mortality in newly imported koi. Fish are more vulnerable after travel due to the fact that they can be exposed to several new environments. Not all koi go direct to koi dealers, many are held in wholesale premises in the supply chain to non specialist aquatic outlets.  The influence travel has on fish depends on how well they are prepared and the conditions in the transit bag as this alters with the length of the journey. Being imported from Japan can lower the pH in the water whereas a short trip from a local dealer may not trigger any change. What is quarantine? Quarantine is the process of isolating new koi to reduce the risk they will introduce parasites or disease to an existing pond of healthy koi. Fish have to go through General Adaptation Syndrome a process through which they attempt to adjust to every new environment they live in no matter how temporary. Acclimatisation has distinct phases; the partial acclimatisation begins by floating fish in a bag or bowl on the pond or tank while the water temperature adjusts.  Full acclimatisation is a much slower process and its length varies from fish to fish.  A new environment can be a challenge resulting in ill health if fish fail to adapt and young fish cope better than mature koi with any change in living conditions. Koi that have fully bonded over many years with their home pond often fail to adapt and it is common for elderly koi not to survive long in a new pond. How can dealers help koi keepers avoid disease? There is no agreed industry standard in the preparation of koi for sale which is why koi keepers need to choose a dealer very wisely. Most dealers carry out some form of quarantine although not all outlets have the facilities. Trade premises need to display both volume and variety of koi to offer customers choice which restricts the space needed for quarantine.  The minimum any dealer should do before selling koi is to check their fish for parasites and treat if necessary. The mucus layer is part of the immune response and, if removed by treatment, should be allowed to regenerate before the koi are sold.  If this was a common practice by all dealers, koi would be better supported after sale. It is the koi specialists who undertake a more thorough quarantine and those who heat ramp their koi are taking further precautions. Heat ramping takes time and costs money and there are dealers who do not follow the practice.  I have never suggested heat ramping is a fool proof method of preventing serious disease in koi ponds.  However, in research in respect of KHV, I have proven that the more heat ramping cycles koi have been through, the fewer koi will later test positive for the virus. I am aware of dealers who use heat alone without any chill cycle who suggest this provides the same result.  However, in all the years of research I have carried out, heat alone does not limit the number of positive tests results in respect of KHV.  Other diseases can also emerge in heat ramping and it is safer that this happens in trade premises than a koi keeper’s pond. Is home quarantine practical? It is impossible to quantify the potential risk carried by one koi. Serious hobbyists quarantine for a whole year and those that live more dangerously, for a few days.  Anything less than a month is unlikely to be effective against any disease although it might deal with a few parasites. Those opting for the middle of the road approach, isolate for three months and, whilst this is ideal, it is important to see any period of isolation in perspective, it is not the length of time koi are quarantined for that matters.  The real issue is whether the koi have been exposed to sufficient triggers of disease.  In addition, how they have coped with the acclimatisation process is also relevant. It is only when quarantine is understood and carried out to high enough standard that it can ever minimise disease risks no matter where it is carried out. Koi keepers need to follow a protocol for home quarantine for it to be effective.  Space for a tank can be limited although a small pond for quarantine works if it is economic to heat. The bonus is that there is less rush to move koi into the main pond and they can be enjoyed rather than isolated in a tank in a garage. Statistics Statistically, most low level koi losses in the average pond are due to poor living conditions not serious disease.  Untested water parameters, low dissolved oxygen levels, and untreated parasitic infections are very common. Bacterial disease has various forms and more cases are triggered by pond management methods than by the introduction of new fish.  Failure to seek sound advice allows bacterial disease to become a long term problem. A high koi mortality in a 3-4 week period suggests a serious disease. It is easy to blame the last fish introduced to the pond overlooking the fact that a carrier of a disease, such as a virus, may have lived in a pond for years before an outbreak is triggered. One of the current issues is the growth in private sales of koi and those from unknown Internet suppliers.  These sales are adding to the disease risk as the origins and health status of the koi are unknown.  It seems ungrateful to refuse a gift of koi from a friend’s pond, however, they too carry risks. It is a sad experience to lose a pond of koi to any health problem, made even worse if they were family pets. It is a tragedy if, with hindsight, the outbreak was avoidable.  In my experience safe means taking every possible precaution, not settling for half measures.