6 Interesting Facts About Koi Fish

Koi fish are colorful ornamental fish known for their long lifespan, large size, and cultural significance—making them one of the most popular pond fish worldwide.

The ancestral form of the fish is the Amur carp (Cyprinus rubrofuscus), but domestic strains are far removed in appearance from wild carp.

These fish are commonly kept in outdoor ponds or garden water features. They have a rich history in Asian culture dating back thousands of years.

1. Koi Fish Means ‘Brocaded Carp’ in Japanese

Koi fish means “brocaded carp” in Japanese and refers to their colorful, patterned appearance.

Koi is actually the informal name for this species—they are often referred to as Japanese koi or by their Japanese name, nishikigoi. 

In Japanese culture, koi symbolize luck, prosperity, and good fortune. Many people even have koi fish tattoos to represent these qualities.

A koi fish was first displayed in Tokyo in 1914—propelling their popularity around Japan and leading to selective breeding in Niigata.

2. Pet Koi Fish Are Kept in Ponds

Koi fish live in outdoor ponds when kept as pets, though their wild relatives are found throughout Asia.

Koi ponds often include rockwork, waterfalls, and aquatic plants.

Special measures may be needed in winter, such as using an aerator to prevent freezing. You could also move your fish to an indoor pond, though this is rarely necessary.

When selecting fish for your pond, remember that smaller fish will grow over time. A typical koi grows up to 14–18 inches and requires about 250 gallons per fish.

3. Koi Fish Lifespan Is Very Long

Koi fish typically live 25–50 years, though some have been reported to live up to 100 years.

With proper koi fish care, they can live for decades. Water quality, nutrition, and preventive health care all play a role in lifespan.

4. Koi Fish Prices Can Range Dramatically

Koi fish prices vary widely based on size, color, lineage, and pattern.

Small koi typically cost between $8 and $50, while some can exceed $100.

The most expensive koi ever sold was $1.8 million in Japan.

Factors that affect price include:

• Genetic lineage: Highly sought after lineages are more expensive.
• Koi variety: The most popular varieties include Kohaku, Sanke, and Showa.
• Pattern: Steps (colored bands across the dorsal surface of the fish) and symmetry in patterns often can increase the price of a koi.
• Size: Larger fish are more expensive.
• Origin: Imported animals are more expensive than domestically produced animals.
• Number of fish purchased: If koi are purchased in bulk the price tends to be lower. Make sure you can house all the koi you intend to purchase if they are not fully grown yet.

5. There Are Many Different Types of Koi Fish

There are over 100 types of koi fish, grouped based on color, pattern, and scale type.

Koi are divided into 16 groups by Zen Nippon Airinkai (the original koi club), a club that oversees the breeding and judging standards of koi.

Three core colors make up many koi varieties:

• Red (Hi)
• White (Shiro)
• Black (Sumi)

Other colors that are commonly seen include:

• Yellow
• Orange
• Blue
• Cream

Some koi have a metallic sheen called “gin rin.”

It is common for koi to be tri-colored, but they can also be either single, bicolored, or multicolored.

6. Koi Fish Can Get Very Big

Koi fish can grow up to 3 feet long depending on the variety and environment.

Adult koi require about 250 gallons per fish, while large or breeding koi may need up to 500 gallons.

Overall, koi fish make great pets for those who can give them the time and space they need.