Kohaku is judged on its white ground before anything else, so a dull or yellowed base sinks an otherwise good fish. Shops sell them by grade, from pond quality culls up to Japanese imports priced well above ordinary pond stock. Pattern shifts as a koi grows and red can spread or fade, so a cheap small Kohaku is a gamble.
In the wild
Red and white carp turned up among food fish in the Niigata rice villages in the early 1800s. The modern variety traces to an 1888 spawning by Kunizo Hiroi, which founded the now extinct Gosuke bloodline. Later bloodlines including Tomoin and Yagozen were built from Gosuke fish crossed with other stock, and those two are the ones still worked in Japan. Nothing patterned like a Kohaku swims wild, since it is entirely a Japanese pond selection.
Good to know
The look is red erythrophore patches over an unpigmented white ground, with no metallic layer under it. Pattern is polygenic and does not breed true, so a Kohaku pair throws white, red and off pattern fry. Keepers judge the edges with two words: kiwa for the trailing edge of a red patch and sashi for the leading one.
Did you know
Japanese hobbyists say koi keeping begins with Kohaku and ends with Kohaku. Beginners buy one first, and experienced keepers come back to it last. Together with Sanke and Showa it makes up the gosanke, the three varieties that lead almost every show standard.
Common questions
Is a Kohaku koi a different species from the Koi?
No. A Kohaku koi is a variety of the Koi, Cyprinus rubrofuscus, and it wants the same tank, water and food as the species.
What size tank does a Kohaku koi need?
A Kohaku koi needs at least 264 gal (1,000 L). It spends most of its time in the bottom.
How big does a Kohaku koi get?
An adult Kohaku koi reaches about 23.6 in (60 cm).
11.8 in (30 cm)119 gal (450 L)39–75°F (4–24°C)
23.6 in (60 cm)317 gal (1,200 L)72–82°F (22–28°C)
6.3 in (16 cm)37 gal (140 L)68–79°F (20–26°C)
5.9 in (15 cm)32 gal (120 L)68–81°F (20–27°C)
4.7 in (12 cm)29 gal (110 L)57–68°F (14–20°C)
23.6 in (60 cm)660 gal (2,500 L)68–79°F (20–26°C)