As particularly valuable fish, different factors including size, bloodline, age, colour and type, determine their worth. Top-level specimens imported from Japan, with a proven bloodline, have been known to fetch more than £50,000 each!
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However, for the average fish enthusiast hoping to start a Koi pond, it doesn't have to cost the earth, as many aquatic centres, water gardens and pet shops sell specimens which are ideal for people new to Koi-keeping.
History
According to experts, China was the birthplace of the Koi carp and not Japan. As a mutation of the common carp, it developed its unusual colouring in its natural habitat in the Caspian, Black and Aral seas of Asia.
Chinese history books state that Confucius's son was given a mutated carp as a gift by King Shoko of Ro. A highly-revered figure, Confucius was a Chinese teacher, politician and philosopher who lived from 551 BC to 479 BC.
When his son received the unusual fish, it became the subject of much Chinese artwork. The species became well-known in China as a result, but despite its beauty, it became a popular delicacy on the dinner table. When the Chinese invaded Japan, they ate the Koi carp as a food source and hence the species was introduced to Japan.
The exact date of when this occurred is unclear, although the first recorded conflict between China and Japan was the Battle of Baekgang in 663 AD.
Carp were viewed as a food source in Japan for many years - the rice farmers bred them as such. It wasn't until the 1820s that the Koi carp was bred in Japan simply for its beautiful appearance, to be admired by fish-keepers.
Valuable specimens
The Japanese breeding programmes of the 19th century successfully transformed Koi carp into the stunning species recognised all over the world today. There are now 22 main types of recognised Koi species, some much rarer than others.
In Japan, they are bred to perfection to bring out their beautiful colouring. The type considered most valuable and sought-after in Japan is a white fish with red spots, as this mimics the colours of the Japanese flag. A white fish with a single red spot on the back of its head is exceptionally valuable, as it's very rare.
Large, mature Koi are also more expensive to purchase than the younger, smaller fish. Koi live to well over 20 years and even up to 50 years old, so some of them are massive. The record for the world's biggest Koi carp is held by Big Girl, a 42kg fish owned by enthusiast Geoff Lawton, of Wiltshire, England. She is 1.25 metres long and eats half a kilo of food daily.
Looking after Koi carp
Koi carp pond fish need more care and attention than other cold-water fish, such as the goldfish. However, it's worth the extra effort to have the stunning fish swimming about outside your home.
If you're planning to set up a Koi pond, don't forget to take into account that the fish are more expensive than goldfish or other cold water species, so ensure you leave enough capital to stock your pond, once you've built it.
As Koi can grow very large, reaching a length of more than 3ft, they need a big pond with plenty of filtration and you'll need to carry out weekly water changes. Remember that large Koi will create a lot of waste, so it's important to monitor the water quality carefully to ensure it' kept clean, as dirty water is detrimental to their wellbeing.
Don't put rocks in the bottom of your pond, as larger fish could snag themselves. Also, place mesh over the pond to prevent predatory animals and birds from trying to eat your fish. Keep the pond away from harsh sunlight, as this creates algae more quickly.
Water quality
It is also necessary to place the appropriate water purifier into the pond before you put the fish in, as tap water isn't of a high enough quality to create a healthy environment for your fish. Check with your local aquarium centre to see which product they recommend.
Routine water changes of 25% of the total volume per week should be carried out in the summer. This can be reduced to changing 10% of the water each week in the winter.
The main reason for doing this is to replenish the mineral content of the water, as this is crucial to maintain fish health. Be careful not to let toxins enter the water - such as chemicals used for tree, shrub or lawn maintenance - as this can kill the fish.
With the right-size pond and proper care and maintenance, Koi carp can thrive as pond fish and bring many hours of pleasure to their owners.
Storage equipment
If you're a Koi carp enthusiast, make sure you have the best storage equipment for your pond-cleaning accessories and fish food.
Solent Plastics? range of airtight plastic storage boxes and trunks would be ideal. If you can't find exactly what you're looking for on our website, please contact us for help and advice.