Koi Quarantine Tanks / Koi Holding Tanks & Koi Vats Whether or not to quarantine has always been a controversial topic amongst Koi enthusiasts, but we must ask the question of ourselves "how lucky do I feel ?", because not quarantining any new fish is taking a significant risk with the rest of your Koi. There is always a risk that you will introduce a potentially dangerous infection into your pond with devastating, heart breaking and not to mention costly, consequences.
In an ideal world we wouldn’t need to quarantine, but how confident are you that the source from which you acquired your new Koi has quarantined it? All reputable dealers will do this, as they rely upon maintaining their good name and generating repeat business, but it’s ultimately up to the individual hobbyist to decide. For the inexperienced, I believe that this is a very difficult judgement to make. In the final analysis I believe that it simply boils down to risk assessment, and deciding what level of risk you as a Koi keeper are prepared to take.
Another reason for quarantining would be for post Koi show observation, particularly if your fish have been in a Japanese style show, mixed with other hobbyist’s fish. An efficient quarantine system will also act as a good "growing-on" system for smaller Koi, when not being used as a quarantine system.