Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Cyprinus carpio


Koi, Cyprinus carpioKoi, Cyprinus carpio
Photos by Andy Rapson


Cyprinus: Latin, cyprinus = carp

General Notes:

Koi are specially bred for their colour, all the different varieties are the same species. They have been bred in captivity since the fifth century when wild carp were first aqua-cultured for food in China. But it wasn't until the 1820's that the fish were bred for their colour in Japan. Koi are not suitable for an aquarium, they really need to be housed properly in a pond of at least 9,000 litres with a minimum depth of four feet. The pond should also have very good filtration with out which you will never see them. In good conditions a Koi could reach 90 to 120 cms (18 - 24 inches) in two to three years, so even a large aquarium isn't suitable.
Depth is also important because Koi need to swim in three dimensions in order to keep their muscle tone around their swim bladders, again this isn't possible in an aquarium. They also need to have seasonal variations in temp and daylight hours in order to maintain their body clock. Without this they may come in to breeding condition at the wrong time and risk egg binding. Finally Koi need to have a phase where they semi hibernate and reduce their activity and feeding. If kept artificially warm they will not live as long. When kept in an outdoor pond the Koi need some form of shade, without this they are at risk from sunburn and the pond is at risk from the dreaded green water. As a rough guide approx 33% of the surface should be in shade.


Koi will eat everything offered. Most Koi are fed on a basic diet of pelleted food which has been specially formulated for them. They will also eat any worms, crustaceans and insects that they come across along with aquatic plants and algae.


Male koi are smaller and less plump than female koi when adult.


Koi are egg scatterers and do not exhibit any brood care. They come in to breeding condition in late Spring to early Summer. The male usually chases the female through the vegetation where the eggs and sperm are released. Both parents will eat their own eggs if they find them.

Wild status

Koi have been introduced in to the wild both accidentally and on purpose and in some areas they have become a nuisance.

Information at a glance

pH: 7.2 - 7.8
dGH: 5 - 12
Temperature: 3 - 28°C (35 - 82°F)
Diet: Omnivore
Size: 100cm (39.5in)
Min tank size: 9,000 litres - pond
Difficulty level: Intermediate
Aquarium type: Community
Swimming level: All levels

Distribution and habitat

distribution map for Cyprinus carpio

Origin: Koi do not have a wild range. Artificially introduced worldwide with the exception of Antarctica

Habitat: Ponds, lakes and canals where they have been introduced.


Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Cypriniformes
Family: Cyprinidae
Genus: Cyprinus
Species: C. carpio, Linnaeus, 1758

Common name:

Carpio carpio gibbosus, 
Carpio vulgaris, 
Cyprinus acuminatus, 
Cyprinus alepidotus, 
Cyprinus angulatus,
Cyprinus atrovirens, 
Cyprinus bithynicus, 
Cyprinus carpio anatolicus,  Cyprinus carpio aralensis, 
Cyprinus carpio brevicirri,  Cyprinus carpio carpio, 
Cyprinus carpio caspicus, 
Cyprinus carpio communis,  Cyprinus carpio elongatus,  Cyprinus carpio fluviatilis,  Cyprinus carpio lacustris, 
Cyprinus carpio longicirri,  Cyprinus carpio monstrosus, Cyprinus carpio oblongus,
Cyprinus carpio specularis, Cyprinus carpio var. gibbosus, Cyprinus chinensis, 
Cyprinus cirrosus, 
Cyprinus conirostris, 
Cyprinus coriaceus, 
Cyprinus elatus, 
Cyprinus festetitsii,
Cyprinus hungaricus,
Cyprinus macrolepidotus,
Cyprinus macrolepidotus,
Cyprinus mahuensis,
Cyprinus melanotus, 
Cyprinus nigroauratus, 
Cyprinus nordmannii, 
Cyprinus nudus, 
Cyprinus regina, 
Cyprinus regius,
Cyprinus rex, 
Cyprinus rexcyprinorum, 
Cyprinus rondeletii, 
Cyprinus specularis, 
Cyprinus thermalis, 
Cyprinus tossicole, 
Cyprinus viridescens, 
Cyprinus vittatus