Koi are ornamental varieties of the common carp that are kept for decorative purposes in outdoor ponds. The origin of the breeding of colour mutated koi dates back hundreds of years in China. These fish grow very large and it is common to see 1 meter long koi and even bigger fish.
The natural ability of the carp to adjust to varying water conditions and temperatures makes this fish fairly easy to keep. Different colour variations have different names. Prices for these fish can easily reach thousands of Dollars per fish.