This article was first written for and published by Koi Magazine in 2007
Quarantine is enforced isolation, usually to contain the spread of some kind of disease considered dangerous. The word, which comes from the Italian quaranta giorni meaning forty days, originates from the 40 day period of isolation of ships and people before entering the city of Dubrovnik in 1377 and was to prevent the spread of the plague, or Black Death.
The quarantining of new koi has always been a recommended practice as prevention against the spread of common parasitic and bacterial infections and has become even more important in recent years since the worldwide spread of Koi Herpes Virus (KHV). Koi, like all animals, can suffer from and carry disease and an apparently healthy fish may be harbouring some form of disease that may pose a risk to any existing population.
A good quarantine regime is as important, if not more so, to koi breeders and dealers as it is to hobbyists. All koi farms need to bring in new brood stock to continue the improvement of the quality of the koi they produce. For this reason they need to follow the same basic quarantine procedure as any hobbyist. Farms which buy fish in to grow on and resell at a later date need to be doubly sure that these new fish are free from disease, as they will most likely be mixed with existing stock before being sold on. Dealers have the same responsibility to their customers as breeders do to ensure that they have done everything that they can to provide properly quarantined fish that are as disease free as can be reasonably expected and should always carry out their own quarantine regime every time they bring in new fish to their establishment.
In an ideal world, every koi keeper would have their own quarantine facility and would quarantine every new fish they buy before introducing it to their pond. If money and space were no object, a hobbyists quarantine facility would consist of a separate insulated building housing a dedicated quarantine tank of approximately 2000 gallons (this would comfortably cope with any size fish that would be purchased), including a bottom drain leading to a more than adequate filtration system. The filtration needs to be able to react to large fluctuations in fish stocking density and medications. The system should include a UV to help reduce the bacteria count within the circulated water and there should be a dedicated air pump to provide adequate aeration during medication procedures. Ideally, the pump should be drawing air from outside the building. Either the air inside the building or the water should be heated (heating the air reduces any condensation in the building). The building should have its own water supply and be equipped with its own nets and bowls. Gloves should be used at all times when handling fish, water or equipment in the building so as to reduce the risk of transferring any disease to any other ponds. The system should have some naive fish, (healthy fish not previously exposed to KHV) “Canary koi”, which serve the purpose of keeping the filtration system active, provide company for any new fish introduced and which also act as indicator fish should any viral disease be present in the introduced fish.
For the great majority of koi keepers however, the next step down from the full quarantine building would be to have a dedicated tank of 500 gallons or more and filter system that can be insulated to enable temperature ramping to be carried out. The drawback is that the tank will have to be covered to retain the heat and therefore observing the fish’s normal behaviour becomes more difficult. The other alternative would be to buy a collapsible tank. This has the advantage that it can be stored away when not in use.
To filter a 500 gallon tank my personal recommendation would be to use something like an Evolution Aqua Eazy Pod, which is designed to cope with a 2000 gallon pond (maximum) and will therefore be better able to cope with unusual stresses that it will be placed under. This should be used with a pump that will turn the pond volume over in a period of 1 – 2 hours. The UV should be a minimum of 30 watts, with a 40 litre per minute air pump providing aeration to the pond. There are several ready made packages on the market and as long as you can find one that meets as near as possible these requirements you should be fine. If you have the skills to make your own quarantine system, you could build something tailored to your own personal needs that can fit into the space that you have available and should only cost a few hundred pounds.
Tap water should, ideally, always be passed through a de-chlorinator before it goes into a pond with fish in it since tap water can contain high levels or chlorine or other chemicals which can harm the fish or filter. The ideal water quality parameters would be undetectable ammonia and nitrite levels (below 0.05 when using a digital meter) and nitrate levels of less than 10 ppm with pH in the region of between 7.5 and 8. This is what would be ideal in any pond.