The Importance of a Quarantine Tank

By Linda Montgomery, KHA

Editor’s Notes in [Brackets] by Nancy Moore, KHA

You should never consider adding a fish to your pond unless it has been adequately quarantined! In order to protect your fish from infection or disease you need to prevent the introduction of new pathogens. The object of quarantining is two-fold: it allows the hobbyist to isolate and treat new fish and it gives those same fish a chance to settle in to a new environment after the stress of handling and shipping.

Why is it so important to quarantine?

All koi and goldfish carry disease pathogens and parasites. It is impossible to medicate your fish to the point that there are no more parasites on them. The best you can accomplish is to ensure the health and strength of both the fish and the environment.

Fish, like all creatures, develop a specific immunity against the pathological agents (bacteria, fungal, or other micro-organism that will harm them) in their own pond. They become accustomed to them. The best explanation of this is in one of the best books out on koi right now, Living Jewels. It explains that there is a “mutual agreement between the koi and the organisms that live on it and around it in a common environment, just as there is a mutual understanding between our bodies and the biological organisms that live on us. We are very dependant on these friendly creatures, but if our resistance is lowered for some reason the friendly bugs can explode in population with a resulting infection.”

When you introduce new fish from other regions, they bring with them bacteria and micro-organisms to which they have become immune, but the fish in your pond are not, as they have not been previously exposed to these same bacteria. The new fish, in turn, may not have been exposed to the bacteria and microorganisms in your pond that your present fish have become immune to.

What basics should the proper quarantine tank have?

There are several important factors to remember when planning a quarantine tank. It should be durable and have a minimum of 150 gallons if you have a smaller pond system and at least a 500-gallon capacity for larger systems. Dr. Eric Johnson says it perfectly: “Larger is better in regard to tank size and will increase your success rate. (‘No wonder my fish died, it was 14 inches in a 30 gallon aquarium!’) If you cannot provide a large, roomy hospital tank, you are completely screwed.” He has such a way with words! On a more serious note, the fish will be much more secure and be less inclined to jump if you make your tank depth at least 2 ½ feet; however, you will still need to firmly cover the tank with bird netting to prevent fish loss.

No quarantine tank should be without a submersible (300 watt) aquarium heater and an air pump. When treating a sick fish, there are few things more important than heat (ideal temperature: 74-78 degrees), aeration and circulation in the tank. It is also recommended to provide some sort of hiding place for the fish (a piece of Styrofoam works great), and make sure that there are no sharp objects in the tank that could injure your fish.

You should have a working and cycled filtration system on your quarantine tank before adding any fish. It is extremely important to do your daily water quality checks

(especially [KH] and pH), after introducing new fish. The pH should ideally be at or above neutral (7.4) [and the KH at least 80 ppm]. Also check ammonia, nitrite, and carbonate hardness often]. Adding crushed oyster shell (in a nylon sock) should raise [general, meaning calcium and magnesium] hardness [if that is necessary] and clarify the water, enhancing fish health. It is also recommended to add non-iodized salt, fit for human consumption, at the rate of 2.5 pounds per 100 gallons, which will achieve a 0.3% salt solution. The salt should not be added all at one time; instead, add a third of total amount each day over a three day period. This is one of the least stressful medications on your fish, will increase the slime coat, will kill a lot of parasites and also helps the fish with osmoregulation. However, salt, like any medication, should only be used for a period of time (14-21 days generally) and then removed with water change outs. [Many koi keepers add a lower level of salinity for a week or two; some only add if fish show signs of stress.]

Keeping excellent water quality perimeters are extremely important in the quarantine system. One of the most important ways to keep and increase good water quality is to do regular and frequent water changes on your system (being sure to add the correct water conditioners after each change out, of course!). [Our club suggests a change-out of 5-10% weekly; unless your pond is on well water, you will need to add a de-chlorinator prior to the new water.]

How long should I quarantine?

There is no set amount of time to quarantine, but a good general rule of thumb is between 30 and 90 days. The length of time necessary primarily depends on water temperature (higher the temperature, the shorter the quarantine period), and also the specific pathogens involved. [At least 30 days with temperatures of 75-76 degrees is recommended to rule out Koi Herpes Virus, KHV.]

[Caution: You are taking extreme risk with your whole collection of koi if you fail to quarantine! Remember that you are ultimately responsible for the health of your fish and should never rely on anyone else to quarantine for you! Even the most responsible, respectable and well meaning hobbyist or koi dealer cannot totally guarantee that a fish is not a carrier of a pathogen or parasite.]