Quarantining Your New Koi

By: Bryan Bateman, AKCA Certified Koi Health Advisor

Congratulations on your new acquisition! With proper care, your koi should give you many years of enjoyment. This care begins right now. Please read thru this explanation of quarantining, the importance of which cannot be over emphasized.

Why Quarantine?

We practice quarantining for a few reasons.

  1. It gives us the opportunity to observe our new koi up close and personal. It is highly susceptible to disease or parasite attack when it is under stress, which it is right now due to the moving and change of environment.
  2. Due to its susceptibility to disease and parasite attack, we don’t want to expose the rest of our fish to this should it happen to break out.
  3. Even though the fish in your pond may appear healthy, there may be some low-level pathogens in your system that your koi have become immune to. Placing a new (stressed) addition to your pond exposes it to these pathogens and increases the likelihood of a breakout.

What is a Quarantine tank?

Ideally, it is a miniature version of your pond. This includes proper aeration and filtration, with frequent water changes. The size of a quarantine tank depends upon the fish load. It could be as small as 50 gallons for one or two small koi, or as large as 1000 gallons or more if it is to hold several large koi. The important thing is that it must be capable of maintaining near-perfect water conditions.

Filtration for a Quarantine tank:

The filter need not be as sophisticated as the one commonly used for a larger pond system. Small filters can be obtained at a reasonable price from pond supply or garden supply shops. It should include both mechanical (to remove solids) and biological (to remove ammonia and nitrites) capabilities. In larger quarantine systems the mechanical and biological systems may be separate units.

The tricky part here is biological filtration. As you may know by now, it takes several weeks for a bio-system to “set up”. Certain types of bacteria must be present to convert ammonia to nitrite and nitrite to relatively harmless nitrate. The fastest way to quick-start a bio-filter is to use some media from your existing system. Commercial bio-system starters have not been proven effective, and are not recommended. Many hobbyists keep a quarantine tank active throughout the year by keeping a few koi in it. This keeps the nitrifying bacteria active and capable of colonizing quickly with the addition of more fish.

You should run your filter with a pump capable of circulating the water once every 30 minutes. If you use a submersible, please place it in a net bag to prevent injury to the koi, who could scratch themselves on it’s sharp corners (when a koi is in an unfamiliar territory, it will tend to dart around nervously for the first day or so) Also be sure to use GFCI electrical connections.

Adding a pond koi to your Quarantine tank:

It is good practice to place one small koi from your pond into the quarantine tank with the new additions. This will expose whatever you have in your pond to the newbies, and also will expose your pond to whatever the newbies may bring with them. Better to discover any incompatibilities now than later!

Water changes:

Due to the higher fish load in most quarantine systems, it is important to do frequent and large water changes. In an extreme situation, where biomass is not available, one could actually maintain a quarantine tank with no filtration if proper water changers are conducted. This would require a 50% water change daily, and regular testing for ammonia and nitrite so changes could be increased if called for. With a proper filter, however, 10 to 15 percent changes twice weekly is recommended.

In either case, you should obtain test kits for ammonia and nitrite. Both of these should be maintained in the zero to .1 ppm range at all times. You should use water which has been de-chlorinated, either by aging or by the addition of sodium thiosulphate at a rate of 1 tbsp per 500 gallons for Chicago area water.

Feeding in a Quarantine tank:

The general thought on feeding in quarantine tanks is that if you are feeding at all you are feeding too much. The point here is that food is the source of most quarantine problems. A koi can easily go two weeks or more without food. You should not feed your Q-tank fish for at least two days after set-up. After this, very small portions of food once per day will be sufficient. Don’t forget to test for ammonia and nitrite. If these levels begin to rise, stop feeding immediately.

Medical care:
So what happens if the koi-in-quarantine develops health problems? Immediate care must be provided if this fish is to survive. If you are able to diagnose the problem, treat according to recommended methods. The entire quarantine tank should be treated, as both parasites and diseases will easily spread to other fish in the system.

If you are unable to diagnose the problem, contact someone who can.  Phone numbers for the MPKS Koi Health Advisors are in every newsletter.

Probably the safest and most effective over-all treatment for quarantine fish is salt. It will kill or at least slow down most parasites, and will also ease the stress level of the koi. If you choose to use salt as a therapeutic, add non-iodized salt at a concentration of 3 lbs per 100 gallons of water. This gives slightly more than .3 ppt salt. Don’t forget to replace the salt at this same concentration with water changes.

How long to Quarantine?
This depends on the condition of the fish, but generally it is recommended to quarantine from 3 to 6 weeks. If all looks good at this point, the fish may be transferred to your pond. With the recent threat of KHV, some have recommended quarantine periods of 6 months or longer.

The best way to test for KHV is to raise the temperature of the quarantine tank to 80 degrees and hold it there for three days. This will generally cause a KHV breakout if your fish has been exposed to it, however there is no guarantee, as some koi may be immune KHV carriers. This is another reason why you should have a small koi from your pond in the Q-tank (hopefully not one of your favorites) – if you bring in an immune KHV carrier, it can still infect another fish.

Happy Koikeeping!