The butterfly koi is a long finned koi, a big pond fish that spends most of its time near the bottom. Butterfly is a fin type, not a color class, so the same fish can be a butterfly Kohaku or a butterfly Ogon. It is best kept by someone with a little experience.
Did you know
The butterfly koi's long fins did not come from a fancy strain. They turned up on plain brown and gray carp living in Indonesian canals and ditches. All the color in a butterfly koi was added later, by crossing those carp into ordinary nishikigoi.
Caring for the butterfly koi
Butterfly koi are pond fish, not aquarium fish. One fish needs at least 264 gal (1,000 L) to start, and a group needs a pond of several thousand liters. They are big, messy eaters and need strong filtration.
The long fins tear on sharp rock and on net frames, and they drag against a strong return. Screen the intakes and smooth any sharp edges. Ragged trailing edges are normal on this form, which makes early fin rot easy to overlook.
Koi handle a very wide temperature range, from 39 to 81°F (4 to 27°C), at a pH of 7.0 to 8.5. They stay active in summer warmth and slow to near dormancy under winter ice. Stable, well oxygenated and well filtered water counts for far more than any narrow target.
Feed a varied omnivore diet of sinking koi pellets and greens, with the odd live or frozen food. They are peaceful and social, and they do fine alone or in a group. Goldfish and other large, peaceful pond fish make good company. They uproot plants and eat anything small enough to swallow.
Breeding them is a moderate challenge. Blue Ridge Fish Hatchery reports that the long fin trait is dominant. Crossing a butterfly back to a standard fin koi does not breed the fins out.
Good to know
A butterfly koi's fins and barbels keep extending as it grows, so old fish look far more extreme than shop juveniles. In Japan they are called onagagoi or hire naga nishikigoi, roughly long tail carp. The English name came from the United States, where Randy LeFever of Blue Ridge Fish Hatchery said they looked like butterflies. Japan's Zen Nippon Airinkai has kept butterfly koi out of competitive judging for many years. American koi clubs added judging standards for them in 2006.
In the wild
The butterfly koi is a cross between Japanese koi and long finned carp from Indonesia. The Saitama Prefectural Fisheries Experiment Station began that work in 1980.
Common questions
Is a butterfly koi a different species from the koi?
No. A butterfly 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 butterfly koi need?
A butterfly koi needs at least 264 gal (1,000 L). It spends most of its time in the bottom.
What does a butterfly koi eat?
A butterfly koi eats sinking koi pellets and greens as part of a varied omnivore diet, with the odd live or frozen food.
How big does a butterfly koi get?
An adult butterfly koi reaches about 23.6 in (60 cm).
How does a butterfly koi breed?
Butterfly koi are a moderate challenge to breed. The long fin trait is dominant, so a butterfly crossed back to a standard fin koi still passes on its long fins.
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)63 gal (240 L)68–81°F (20–27°C)
4.7 in (12 cm)63 gal (240 L)57–68°F (14–20°C)
23.6 in (60 cm)660 gal (2,500 L)68–79°F (20–26°C)