I have apond in my back yard and I put some Koi in it. That's just a group of colored variants of the Amur carp. It's nice. 
Koi fish are beautiful, where did you get them?
Koi
Koi is an informal group of the colored variants of "C. carpio". Several varieties are recognized by the Japanese. Koi varieties are distinguished by coloration, patterning, and scalation. Some of the major colors are white, black, red, orange, 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.
History.
Carp are a large
Cyprinus rubrofuscus
Cyprinus rubrofuscus, the Amur carp, is a species of cyprinid fish. It is widespread in Eastern Asia where native to Laos, Vietnam and China from the Amur to Red River drainages. It has also been introduced outside its native range. It is the wild form of the well known koi. It is known for its muddy flavor and boniness, hence, it is not commonly eaten by locals except when stewed.
In the past it was considered a subspecies of the common (or European) carp