Koi are ornamental varieties of domesticated common carp that are kept for decorative purposes in outdoor/indoor koi ponds or water gardens.
Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, yellow, blue, and cream.
The most popular category of koi is the Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.
Carp are a large group of fish originally found in Central Europe and Asia. Various carp species were originally domesticated in East Asia, where they were used as food fish. The ability of carp to survive and adapt to many climates and water conditions allowed the domesticated species to be propagated to many new locations, including Japan. Natural color mutations of these carp would have occurred across all populations. Carp were first bred for color mutations in China more than a thousand years ago, where selective breeding of the Prussian carp (Carassius gibelio) led to the development of the goldfish.
The common carp was aqua cultured as a food fish at least as far back as the fifth century BC in China, and in the Roman Empire during the spread of Christianity in Europe. Common carp were bred for color in Japan in the 1820s, initially in the town of Ojiya in the Niigata prefecture on the northeastern coast of Honshu island. By the 20th century, a number of color patterns had been established, most notably the red-and-white Kohaku. The outside world was not aware of the development of color variations in koi until 1914, when the Niigata koi were exhibited in the annual exposition in Tokyo. At that point, interest in koi exploded throughout Japan. The hobby of keeping koi eventually spread worldwide. They are now commonly sold in most pet stores, with higher-quality fish available from specialist dealers such as “Bernd’s Pond”.
Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, yellow, blue, and cream. While the possible colors are virtually limitless, breeders have identified and named a number of specific categories. The most popular category is Gosanke, which is made up of the Kohaku, Taisho Sanshoku, and Showa Sanshoku varieties.
New koi varieties are still being actively developed. Ghost koi developed in the 1980s have become very popular in the United Kingdom; they are a hybrid of wild carp and Ogon koi, and are distinguished by their metallic scales. Butterfly koi (also known as long fin koi, or dragon carp), also developed in the 1980s, are notable for their long and flowing fins. They are hybrids of koi with Asian carp. Butterfly koi and ghost koi are considered by some to be not true nishikigoi.
The difference to Goldfish:
Goldfish were developed in China more than a thousand years ago by selectively breeding Prussian carp for color mutations. By the Song Dynasty (960 - 1279), yellow, orange, white, and red-and-white colorations had been developed. Goldfish (Carassius auratus) and Prussian carp (Carassius gibelio) are now considered different species. Goldfish were introduced to Japan in the 16th century and to Europe in the 17th century. Koi, on the other hand, were developed from common carp in Japan in the 1820s. Koi are domesticated common carp (Cyprinus carpio) that are selected or culled for color; they are not a different species, and will revert to the original coloration within a few generations if allowed to breed freely.
In general, goldfish tend to be smaller than koi, and have a greater variety of body shapes and fin and tail configurations. Koi varieties tend to have a common body shape, but have a greater variety of coloration and color patterns. They also have prominent barbell’s/whiskers on the lip. Some goldfish varieties, such as the common goldfish, comet goldfish, and shubunkin have body shapes and coloration that are similar to koi, and can be difficult to tell apart from koi when immature. Since goldfish and koi were developed from different species of carp, even though they can interbreed, their offspring are sterile.
The common carp is a hardy fish, and koi retain that durability. Koi are cold-water fish, but benefit from being kept in the 59-77°F range, and do not react well to long, cold, winter temperatures; their immune systems "turn off" below 40°F. Koi ponds usually have a yard or more of depth in areas of the world that become warm during the summer, whereas in areas that have harsher winters, ponds generally have a minimum of 4½ feet. Specific pond construction has evolved by koi keepers intent on raising show-quality koi.
Koi's bright colors put them at a severe disadvantage against predators; a white-skinned Kohaku is a visual dinner bell against the dark green of a pond. Herons, kingfishers, otters, raccoons, cats, foxes, badgers and hedgehogs are all capable of emptying a pond of its fish. A well-designed outdoor pond will have areas too deep for herons to stand, overhangs high enough above the water that mammals cannot reach in, and shade trees overhead to block the view of aerial passers-by. It may prove necessary to string nets or wires above the surface. A pond usually includes a pump and filtration system to keep the water clear.
Koi are an omnivorous fish, and will eat a wide variety of foods, including peas, lettuce, and watermelon or oranges. Koi food is designed not only to be nutritionally balanced, but also to float so as to encourage them to come to the surface. When they are eating, it is possible to check koi for parasites and ulcers. Koi will recognize the persons feeding them and gather around them at feeding times. They can be trained to take food from one's hand. In the winter, their digestive systems slow nearly to a halt, and they eat very little, perhaps no more than nibbles of algae from the bottom. Care should be taken by hobbyists that proper oxygenation and off-gassing occurs over the winter months in small water ponds, so they do not perish. Their appetites will not come back until the water becomes warm in the spring. When the temperature drops below 50°F, feeding, particularly with protein, is halted or the food can spoil in their stomachs, causing sickness.
One famous scarlet koi, named "Hanako", was owned by several individuals, the last of whom was Dr. Komei Koshihara. Hanako was supposedly 226 years old upon her death in 1977, based on examining one of her scales in 1966. Koi "maximum longevity" is listed as 47 years old.
Disease: Koi are a very disease tolerant derivative of the carp family. With proper care they resist many of the common parasites that effect more sensitive tropical fish species such as tricodina, epistylis, ick and other cilliated protozoans common in the tropical fish industry Viral Diseases KHV Koi Herpes Virus and SVC -Spring Viremia of Carp are a major concern to both the Ornamental fish industry and the Food Fish Industry. SVC has been found on an ornamental koi fish farm in Kernersville NC in 2002 and required complete depopulation of the fish stocked and a lengthy quarantine period. The protection from this disease has triggered one koi farm in Florida to isolate itself from these diseases by choosing not to import fish from any source and to focus on producing high quality koi, butterfly koi and goldfish on their premises. KHV - Koi Herpes Virus is a Herpes Virus that is transmitted though contact or close proximity of infected fish typically at water temperatures above 72 degrees. There is no know cure for KHV.
One Reason, “Bernd’s Pond” only carries koi from an proofed over 30 yearlong healthy population.
Like most fish, koi reproduce through spawning in which a female lays a vast number of eggs and one or more males fertilize them. Nurturing the resulting offspring (referred to as "fry") is a tricky and tedious job, usually done only by professionals. Although a koi breeder may carefully select the parents they wish based on their desired characteristics, the resulting fry will nonetheless exhibit a wide range of color and quality
Koi will produce thousands of offspring from a single spawning. However, unlike cattle, purebred dogs, or more relevantly, goldfish, the large majority of these offspring, even from the best champion-grade koi, will not be acceptable as nishikigoi (they have no interesting colors) or may even be genetically defective. These unacceptable offspring are culled at various stages of development based on the breeder's expert eye and closely guarded trade techniques. Culled fry are usually destroyed or used as feeder fish (mostly used for feeding arowana due to the belief it will enhance its color), while older culls, within their first year between 3" to 6" long (also called "Tosai"), are often sold as lower-grade, pond-quality koi.
The semi randomized result of the koi's reproductive process has both advantages and disadvantages for the breeder. While it requires diligent oversight to narrow down the favorable result the breeder wants, it also makes possible the development of new varieties of koi within relatively few generations.