How to acclimate a Koi fish

Acclimation is the process of gently introducing a Koi into a new environment.

There are many reasons why you may need to acclimate a Koi fish into a new pond or tank.  You may have purchased a new Koi and are bringing it home to a quarantine tank.  You might have to bring your Koi indoors in the fall.  Other reasons include:

  • Moving a sick Koi to a hospital tank
  • Moving to a new house
  • Your fish is a Koi show entrant


The most important factor when introducing a Koi into a new pond is equalizing the temperature of the bag water with the water in the pond or quarantine tank.  A sudden temperature change will interfere with your Koi's metabolism and could possibly kill the fish.  Slowly acclimating the fish will allow their metabolism to accommodate the change in temperature.

A Koi fish can withstand a 20 degree Fahrenheit temperature swing during acclimation.  A larger difference in temperature should be avoided.  Consider adjusting the temperature of the new body of water the Koi will reside in to bring it within 20 degrees F of the old pond.  It is easier for a Koi to adjust to a warmer temperature than for it to adjust to a colder temperature.

Acclimation Steps

  1. The pond or tank the fish is going into should have pristine water quality.  Moving and acclimating a Koi is hard enough without having to deal with poor water quality.
  2. Float the bag or tub the Koi is in for 1/2 hour (longer if the temperature change is greater than 10 degrees F)
  3. Scoop the Koi out of the bag with your hands or a sock net.  Do not use a regular net, it will strip off the slime coat when you raise the fish out of the water.
  4. Discard the bag water.  Do not dump it into the pond, it contains fish waste and the water will have unstable pH level.
  5. Cover the tank with a net.  Koi are jumpy when their surroundings change.
  6. Place one or more (depending on the size of the tank or pond) pieces of Styrofoam that are one to two square feet in size over the net.  This will provide a place for the Koi to hide under while they are adjusting to their new home.

Old Style

If you're thinking, "Wait a sec, aren't I supposed to slowly introduce the Koi to the new pond water?", then you are partially correct. The old school of thinking was:

To float the bag for 20 minutes, open it up and then add 25 percent water.  Repeating until bag barely floats and then releasing the Koi.


Dump the water and the Koi into a tub.  Float the tub in the pond and slowly add water for half an hour.

Now the general consensus (see Koi Kichi) is that equalizing the temperature and getting the Koi out of the foul bag water as soon as possible is better than equalizing all of the water parameters before introducing a Koi into your pond.  A quick pH change is thought to do less harm than having the Koi immersed in water that is high in Ammonia and CO2 for an extended period of time.



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