Koi
The major named varieties include:Goldfish (金魚) 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, though, 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, but a subspecies, and will revert to the original coloration within a few generations if allowed to breed freely.
Lionhead (goldfish)
Lionheads are sometimes sensitive to low water temperatures. Due to their slow nature, they should not be kept with faster moving fish such as comets, common goldfish, and shubunkins. If kept in an aquarium, the recommended tank size for one fish is 20 gallons with double filtration. They are social fish so tank mates are recommended. They should be kept in a species-only tank with other goldfish. It is advised to feed goldfish only sinking food because flakes can cause swim bladder issues. Lionhead goldfish are omnivores so they thrive on a diet rich in plant and animal matter. High-protein diets will make their colors more vibrant and will cause greater growth.