The Koi (or "Nishikigoi" in Japan) are becoming quite popular in the United States for breeding. But only few people really know where and how they came to be. The first Koi resulted from the breeding of the Asian carp and the German carp. After years of careful selective breeding, different color mutations started showing up. The earliest patterns in color were recorded in 1805. To this day, thousands of color variations and combinations can be seen.

Popular colors include white, yellow, black, silver, orange, blue, red and green. There are countless possiblities of color combinations. Each Koi have their own name, and these names are based on their color and pattern. There may be a difference in the favorite types, which depends on the location that they're in.

These fish are being raised for sale in various countries, like Japan, Singapore, Israel and the warmer states in the U.S.. The fish can be bought at many of those local pet stores. If there's no stock available, the buyer can choose to order the fish. By ordering, the advantage of this is that the buyer will have more options, since they don't have to pick from the stock on hand. On the other hand, the disadvantage of this is that the buyer won't be able to pick the specific Koi that they want to have.

Unlike most of the other fish out there, they will continue to grow up to the point that they will reach their maximum size (and it doesn't matter where they're being placed). The infant ones are in lengths of 3 inches, while the biggest ones can reach around 3 feet or more! They commonly grow around 2 feet in length. As for their age, they have been known to live up to 30 years old (under the right conditions), the oldest of which have lived up to 233 years!

The Koi are omnivorous, feeding on both meat and plants. This determines the versatility of the Koi's diet. They'll eat almost anything you give them, and it doesn't matter if its good for them or not. The owner should be the ones to control what and how much they eat, because they are incapable of judging what's right or wrong for their diet, and the amounts that they should be taking on a daily basis as well. The healthiest treats for them are the natural food, like earthworms and tadpoles, and food like bread, lettuce, fruit and veggies.

Owners should take necessary precautions when feeding them with beans, corns and grapes, as these food contain an outer casing, which can't be properly digested by the fish if eaten by them. Outer casings of these food should be removed before feeding.

The Koi are non-aggressive fish, and they are able to mingle with other fish like the comet and goldfish. As they are fast eaters, the Koi will eat any fish that they will find smaller, and this could be a problem! The Koi do not have teeth, that's why they can be fed through their owner's hand (which can be a great past time for their owners too)!). For this, Koi breeding is really a fun hobby for fish lovers out there!