VARIETIES
This time around many koi varieties came out which sometimes we have a hard time to identify them.  Not like at the begining koi are developed in a single species the Common Carp. easy to identify. However with various mutations and crosses. 
Home
Scale Types
Scaled.  The most common fish type with typical carp scales.

Doitsu.  A fish with scales along the dorsal and lateral lines only.

Leather.  A fish with no visible scale, exept possibly very small scales along the dorsal line only.

Gin Rin.  A normally scaled fish which has a gold or silvery mirror like effect on the individual scales. 
Ai-goromo
Asagi
Bekko Butterfly Koi Chagoi
Hariwake
Ginrin
Goshiki Hikarimoyo
Doitsu
Kawari
Hikarimuji Kawarimono
Hikautsuri
Kabuto Daiwa
Kikokuryu Kujaku
Koromo
Kikusui
Kohaku
Kumonryu
Ochiba Tancho
Matsuba
Ogon
Sanke Shusui Utsuri Yamatonishiki
Showa