How To Care For Koi Fish

Care For Koi, And They’ll Live Long!

Care for Koi babyAs any serious Koi keeper knows, care for Koi is not as simple as purchasing goldfish from a pet store and dumping them in a fish tank.

First of all, that fish tank should be a pond with enough room for Koi to grow in.  The minimum recommended stocking rate for any Koi pond is one Koi per 250 gallons of water.  However, for those who wish to care for Koi, particularly to ensure their proper body formation and maximum size potential, twice the amount of water per Koi is recommended.

As mentioned in a previous article, it is better to care for more Koi than less as the fish are “happier” in a populous environment.  This of course, would require increasing your pond volume.

Depending on where in the world one resides, it is good to keep in mind that Koi construction should keep out predators such as birds and mammals.  Shaded trees are thus a good idea to block the view of aerial predators.  To keep water clean of leaves and debris, stringing nets or wires above the surface is also important. This is because care for Koi begins with care for its pond water.

Koi can thrive in water temperatures of 15-25 degrees C (59-77 degrees F).  The optimal temperatures however are at 23-30 degrees C (73.4-86 degrees F).


Pond water should be cycled once an hour for filtration.  It should maintain a pH level of 6.5-9 and measured to keep a 5% salinity at all times.  It should be free of waste material and be non-chlorinated.  Keeping low ammonia levels (due to fish waste) is also necessary for to care for Koi.  An ammonia measurement of one part per million is considered harmful for the fish.

One of many environmental problems which arise in the care for Koi is that of green water caused by algal blooms.  The nitrogen wastes and other chemicals in the pond nourish the growth of algae and cause the pond to darken or become green.  This is not only toxic for the fish but for humans as well.  Hence it is best to regularly test the water for chemicals and install proper mechanical and biological filtration and pump systems.

Care for Koi also includes a healthy Koi diet.  Koi have evolved to be omnivorous fish with a high tendency towards the consumption of benthic organisms, such as water insects, worms, larvae and even Molluscs.  Koi are also stimulated by the variety of eating fruit, shrimp or fish every so often.


Keeping this in mind, however, there are commercial Koi foods that come in pellets or rods for Koi to chew that make guesswork easy.  Koi are known to eat more than necessary for their proper growth so feeding must be controlled.  More food also means, more waste in the water. It is better to feed the Koi in short spurts several times a day than to give them one large feeding.  For aesthetic purposes and in order to give Koi a physical check-up, it would be good to choose food that floats.  When the fish come up to feed at the surface it is much easier to check them then for parasites and ulcers.

In countries where the weather above water drops below 10 degrees C (50 degrees F), it is advisable to slow down the feeding and eliminate protein from their diets.  This is because their bodies cannot process food as much or as fast as in the warmth.

Care for Koi may initially seem a complicated task for first-time Koi owners.  However, its rewards are found in nurturing the healthiest and happiest of these beautiful ornamental fish!

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