6 Interesting Facts About Koi Fish

Koi fish are an extremely popular and colorful form of the fish species Amur carp (Cyprinus rubrofuscus).

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

A koi fish’s bright vibrant colors and behaviors can provide a splash of color and activity to any outdoor pond.

1. Koi Fish Means ‘Brocaded Carp’ in Japanese

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, the koi fish meaning is “brocaded carp.” In Japanese culture, koi fish are often kept since they symbolize luck, prosperity, and good fortune.

A koi fish was first displayed in Tokyo in 1914—propelling their popularity around Japan. This was also around the time selective breeding started in Niigata, Japan, which developed and spread worldwide.

2. Pet Koi Fish Are Kept in Ponds

You may be wondering—where do koi fish live?

While wild koi live in the Aral, Black, and Caspian Seas, pet koi fish are commonly kept in outdoor ponds. Ponds can be great ways to enjoy your koi and even provide a scenic landscape to your property, since they often include elaborate rockwork and waterfalls.

Koi are temperate freshwater fish that thrive in water temperatures between 64–75 F, and can survive to almost freezing temperature at 33 F. An 8-foot-deep pond can maintain a thermocline (temperature gradient) in the water, allowing koi to experience different temperatures.

A deep pond will also make it easier for koi to stay in the pond during winter. Water can freeze anywhere between 18–24 inches deep in a pond. Ensuring your pond is deep enough will prevent your fish from freezing.

During the winter, koi will go into dormancy when the water temperature reaches below 40 F. Their metabolism and activity level will drop slowly, resulting in more time spent on the bottom of the pond and not much swimming.

A pond heater can be added to increase the temperature of the water to ensure koi survive winter temperatures.

Special measures can be taken if your pond freezes over during the winter. For example, creating a hole in the ice and adding an aerator can help your koi survive. You could also move your fish to an indoor pond in the basement or garage.

When selecting fish for your pond, remember that smaller fish will grow over time. Knowing how big your fish will become as an adult is important to determine how many fish can be kept in a pond. A typical koi will grow up to 14–18 inches and will require 250 gallons per fish, regardless of their size.

3. Koi Fish Lifespan Is Very Long

With all the care that goes into keeping pet koi, you will be rewarded with a long-living fish. So how long do koi fish live?

Koi fish can live between 25–50 years on average when provided with the correct environmental conditions. There has been reports of koi living to 100–200 years—the oldest koi ever documented lived to be 226 years old.

Water quality, nutrition, and preventative health care can help improve koi fish lifespan. There are many commercial koi fish foods that are available to pet parents, and can be used exclusively to feed koi and provide complete nutrition.

Providing appropriate vet care can help improve the lifespan of any koi. Not all veterinarians will treat fish, so be sure find a veterinarian who specializes in your pet. Organizations such as the American Association of Fish Veterinarians (AAFV) and can help assist pet parents in finding a vet that has experience treating koi.

4. Koi Fish Prices Can Range Dramatically

Koi can range in price due to many factors. Typically, a small koi will run anywhere between $8 to $50. Some koi, depending on size and color, can cost over $100. The most expensive koi ever sold at auction was for 1.8 million dollars in Japan at the 2017 All Japan Koi Show.

Factors that determine the price point for koi may 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 different types of koi fish that are separated into 16 groups based on Zen Nippon Airinkai (the original koi club), a club that oversees the breeding and judging standards of koi.

Koi can be differentiated by coloration, pattern, and scalation. New varieties of koi are constantly being developed by selective breeding.

Three core colors make up many koi varieties:

1. Red (Hi)

2. White (Shiro)

3. Black (Sumi)

Other colors that are commonly seen include:

• Yellow

• Orange

• Blue

• Cream

Some fish may have a silver or gold metallic sheen to their appearance. Known as “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

So, how big do koi fish get? It depends on the species—some koi fish can reach up to 3 feet long!

In general, koi fish should have 250 gallons of pond space per fish. A pond size of 500 gallons per fish is required for large show fish or reproductively active females.