How to acclimate a Koi fish

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

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


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.



Back to Koi Care.