The domestication of koi fish started as early as the 19th century.

It is believed that koi originated in China. After the Chinese introduced carp fish in Japan, the Japanese began to breed common carp as a food source initially. This marked the beginning of Koi fish domestication.

Butterfly Koi is notable for their long set of fins.

Butterfly Koi originated in mid-20th century Japan. The Japanese breeders crossbred traditional koi to a wild Indonesian longfin river carp. Butterfly Koi can grow around 40 inches (101 cm), it has an oval shape and the body is slender than the original koi. It has long, flowing fins, long barbells, and a hardier breed or more suited to any type of climate.

Kohaku is the first variety of koi that has two colors.

Kohaku is one of the most popular breeds of Koi fish in Japan. It is also one of the most common koi seen in aquariums or ponds. They are known for their white body and red marking, traditionally called hi. There are different varieties of Kohaku, but Tomoin and Yagozen are the only types that remain in Japan.

Karasu is one of the older types of koi fish.

Karasu, which means “crow” in Japanese, has a black body and may either have a white or orange belly. It is one of the older types of Koi fish and believed to bring good luck to the pond.

Koi fish are very sociable.

Koi is a social fish. They enjoy living in groups or pairs. They are also friendly and do not eat or fight with other species of fish when place in one aquarium. Koi, just like other pets, would sometimes come out to the surface if it’s feeding time or to seek a touch or pat on their head from their owners.

Koi fish may live for more than 50 years.

The lifespan of Koi fish depends on their environment and genetics. In the wild, a koi fish may live for approximately 30 to 40 years, while in captivity they may live for around 70 years. Some factors like quality food, and pond filters affect their lifespan.

Hanako was the oldest koi fish.

Reportedly, the red Higoi Koi Hanako was the oldest Koi fish ever recorded. Hanako was born in 1751 in Japan. She died because of old age in 1977 at the age of 226. She spent most of her time in a pond near a small valley in Mt. Ontake in Japan.

Koi fish are omnivorous.

In the wild, koi fish eat bugs, algae, plant and animal matter, and any piece of food that will float in their way. Meanwhile, in captivity, they consume koi food, vegetables, krill (small shrimp), and plankton, cereal, and dead leaves.

Koi fish have teeth.

Contrary to what most people believe, Koi fish have a row of teeth at the back of their throat. This is referred to as “pharyngeal teeth.” Pharyngeal teeth are common to other freshwater fish. They use their teeth to grind food like shells and insects they find at the bottom of the pond.

The most expensive koi fish cost $1.8 million.

The bidding took place in the city of Hiroshima, Japan. A collector from Taiwan bought the female Koi named “S Legend” for $1.8 million. This made it the most expensive fish. It is a red and white koi fish that measures 3 feet and 3 inches or 99.06 centimeters.

A male and female koi fish represents the yin-yang symbol.

Koi fish is often associated with yin-yang symbols or a relational concept in Chinese culture. The black and white tear-drop-like symbols represent two Koi fish, a male and female swimming together. They symbolize two energies that come together as one creating harmony and balance.

Koi fish have different symbols.

In Japanese culture, Koi fish symbolizes good fortune or luck, spiritual and material abundance. It is also associated with the strength of purpose and perseverance during difficulties. While, in Buddhism, Koi fish signifies courage. Whereas, in feng shui, a Chinese traditional practice, the spirit of Koi may attract good luck, spiritual benefits, and fortune.

Koi fish go on a type of hibernation.

Normally, during winter or if the water temperature is below 10ºC or 50ºF, Koi fish will go into a type of hibernation called torpor. It is a short-term kind of hibernation, and usually lasts for several hours to weeks. During this time, their metabolism and protein synthesis is slow. They eat less and they huddle together for them to keep warm.

An ancient Japanese and Chinese myth tells how a koi fish turned into a dragon.

An ancient Japanese and Chinese myth tells how a Koi fish became a dragon. In the story, a group of Koi swam in the Yellow River located in China. They gained strength as they swam against the current of the sea. However, when they reached the end of the river, several Koi fish turned back and just let the flow of the river carried them.

The remaining Koi continued to swim. They tried to reach the top of the waterfall. These Koi fish kept trying for 100 years. Finally, one Koi leaped and reached the top of the waterfall. The gods recognized the Koi for its perseverance and turned it into a dragon.

Ghost Koi is of British origins.

Unlike other koi types, Ghost Koi originated in Britain. Ghost Koi is a crossbreed between a mirror carp, a type of fish common in Europe, and a metallic Ogon Koi. The name Ghost Koi comes from their ghostly appearance when they swim, their metallic scales make them apparently disappear when they are underwater.

Koi eat their eggs and young.

Generally, it is possible for Koi fish to eat their eggs and offspring or fry. However, it is not because Koi fish are aggressive or because they can attack other fish. It is because they sometimes mistakenly see their eggs and young as insects.

Koi tattoos are very popular.

Gold or a combination of orange, silver, and black are some of the most colors used in choosing a koi tattoo design. It is commonly placed with other Asian symbols like lotus flowers, or other Chinese characters. Why are they so popular? It is believed that a koi tattoo symbolizes strength, a person that has it can overcome any struggle.

A crowded pond will make the koi fish unhealthy.

Koi fish do not require a lot of maintenance. One important thing that owners need to observe is that the pond should not be overpopulated to ensure that Koi fish will remain healthy. Though plants are good for the pond, it is also important that there aren’t too many plants covering the surface of the pond. There should be at least a ratio of 40 to 50 percent plants to water. Too many plants may prevent sunlight from getting into the water and may affect oxygen levels.

Marble betta or koi betta has blotches all over their body.

Koi betta or also marble betta is a type of koi that has blotches or spots in the body. They have special genes called “jumping genes” or “transposons.” This is a genetic trait that causes their color to change throughout their lives.

A combination of 8 red and 1 black koi fish is "lucky."

In feng shui practices, 8 is a prosperous number. A combination of 8 red and 1 black koi fish symbolizes prosperity, good fortune, and energy. At the same time, paintings of a koi pond with colorful koi fishes are also popular feng shui artwork and are said to bring good luck. Display these paintings on the east, southeast, or north walls of your home for maximum effect.