Koi are the domesticated variants of the Amur carp and now are one of the most expensive fish species in the world. It’s not a surprise to find kois in outdoor fishponds or water gardens for decorative purposes as a sign of wealth. Being kept mainly in ponds drives the koi’s unique coloring and patterns which appear better from a top view of the fish. This is in comparison to another decorative fish, the goldfish, whose color and patterns appear better from the side when viewed in an aquarium.

Koi breeding is taken very seriously to bring out preferred colors and patterns as the resultant fish can be worth millions. The most expensive koi, which is also the most expensive live fish ever sold went for a staggering $1.8 million – equivalent to four Lamborghinis Aventador. The vibrant colors of a koi originate from the color cells in their skin which come in red, yellow, black, white, blue, or metallic. The cells also have different depths in the skin, with those closest to the surface leading to brighter coloration and being worth more. However, with all those color combinations, prize-winning koi are usually from the Kohaku, Sanke or Showa varieties.

Breeding koi is an arduous and painstaking process with each koi releasing thousands of eggs at a time. The amount is carefully reduced, with one breeder going from three million eggs to 15 thousand fish the first year. From that, one thousand fish will be chosen in the second year, and the numbers will continually reduce into adulthood. However, with such a price tag on the best koi, the cost is well worth it.