The Koi Fish

If you want to keep Koi it is essential that you know the animal you intend housing as part of your life.We are not talking about the intimate details that go into understanding the minutia that go into making a show quality Koi which is a journey of learning that spans many years. Rather we are talking about the very fundamental basics required to keep Koi alive in the first place.

There is much myth that surrounds the Koi, bordering on the near fantastical. Much of it has grains of truth but equally much of it is utter nonsense.


The scientific name for Koi is cyprinus carpio. Genetically identical to the common carp Koi are simply selectively bred fancy brocaded carp that over the last 230 years or so have been crafted and honed by the Japanese master breeders for their unique and colourful patterns. 

Size is greaty prized amongst Koi keepers. Today's Koi are specifically bred for size first, with colour and pattern a distinct second. It is not uncommon to see a Koi of two years of age hit a size of 60cm+...

A typical minimum size for an average Koi is around 70cm with a large percentage going to 80cm+. These are not goldfish you are dealing with. A full grown Koi is an imposing animal and it is when they are full grown that their power and grace is at maximum impact in your Koi pond.


It is a common fallacy that Koi will only grow to the size pond they are in. It is simply not true.  Koi with the genetic potential to hit 80cm will do so in a bath tub.

Hence your Koi pond has to be able to accommodate your fish when they are fully grown. As such a minimum size of 10kl is recommended for Koi ponds, preferably bigger.

One Koi per 1000 litres of water is a good rule of thumb for fish under 60cm. Above 60cm one fish per 2000 litres of water is a good rule to observe.

Koi can live for decades. The oldest fish we know of in South Africa is over 40 years of age and still going strong. Hence your Koi pond should be built with this kind of time frame in mind.

Koi are gregarious temperature driven feeders. They are affectionately known as water pigs and even when fully grown will easily consume 1% of body weight of food per day in warm water. At lower temperatures they consume correspondingly less.

The load a large Koi can place on your filtration system can be significant. It is thus of vital importance to ensure that your filters are able to handle this load.

Koi are intelligent and friendly creatures. They can and do become pets in the real sense of the word. Your Koi pond should thus focus on your Koi first, and as a result on your filters first and foremost.