The Koi come in a wide array of colors. The black Koi are distinguished from the other varieties with their own coloring, and nothing more. They can live up to 35 years, but the oldest of them have lived around 200 years! They are seen regularly in outdoor ponds throughout the globe.

The male Koi are recognized and distinguished by their concave anal section, and their breeding spots on their head. They can lay up to 1,000 eggs. The fry (baby Koi) will start emerging within around 4 to 7 days, depending on the temperature condition of the water. It's an amazing fact that their color emerge when they're 3 to 12 weeks old. At the start of their breeding in Japan from carp mutations, they only had two colors. More and more colors appeared due to breeding, which showed a variety of magnificent patterns and colors.

They can grow up to about 36 inches long, that's why they should be kept in large ponds. The species known as the Magoi is considered as one of the first black mutations which can reach to great sizes in length. Their color is actually deep bronze, but seen as black when viewed from above. Due to their unique possibilities in terms of size, the blood of the Magoi is being re-introduced to the other species so as to maximize their potential when it comes to growth.

The Karasu ("karasu" which means "crow" in Japan) is one of the extremely old species of black Koi. It is characterized by its black fins and body. It can also have an orange or a white belly.

They can also have the ability to change color which is triggered by the environmental or dietary effects. The color changes range from duller to brighter shades. The Matsukawabake is known for this characteristic; black in color and has areas or white on its body. Depending on the water's temperature or the season, its color can completely change. It can turn completely black or white, and will go back to its original color once the temperature conditions will change.

The Kumonryu ("kumonryu" which means "dragon fish"), which first appeared in the 1980's, is considered to be as the most popular of the species. They are called as such as it is reminds people of the bodies of dragons depicted in ancient paintings (others would say they look like dragons ascending through the clouds). This can also alter their colors.

Pond owners are being attracted to the Koi's colors and patterns, and there's nothing more exciting than owning a fish like the black Koi that can change their color right before your very eyes!