Common Name(s)
Koi Fish, Koi Carp, Nishikigoi
Scientific Name
Cyprinus Carpio
Calm, non aggressive.
Maximum Size
Usually around 3 feet, but it depends on the breed.
Minimum Tank Size
1000 gallons
Tank Setup
Koi are pond fish. They need a pond that is at least 1000 gallons, preferably 1500 or more.
Tank Region
Middle-bottom. They come up to the top for food.
Koi are omnivores. Feed high quality floating pellets.
Difficult. Koi breed in the spring and they need a round breeding pond that is at least 1000 gallons.
Koi are coldwater fish, so only keep them with other coldwater fish. They do well with single tail slim bodied goldfish such as common goldfish and comet goldfish. Don't keep koi with fancy goldfish.
Ease of Keeping
Pretty easy.
pH: 7.5 is ideal, but it dosen't really matter just as long as it is stable. Koi do good at a temperature between 59 and 77 degrees fahrenheit. When the temperature drops below 45 degrees in the winter, they go dormant. They just go to the bottom of the pond and they stop eating.
Koi live for a long time. The oldest koi lived to be 226 years old.

By Arden - originally posted to Flickr as Wow, CC BY 2.0,