Butterfly Koi: What They Are and How to Care for Them

Butterfly Koi Behind Short-Finned Koi

A dark butterfly koi swims behind traditional koi.

Butterfly koi float through your pond like graceful dragons, trailing a beautiful shadow of long fins behind them. Their unique look make them a joy for pond owners who want to add something a little different to their backyards.

Butterfly koi look and behave much like their short-finned cousins. That means they can fit in seamlessly with just about any fish population.


At a Glance: Butterfly Koi

  • Butterfly koi are a cross between traditional koi and long-finned carp
  • Butterfly koi have longer fins and skinnier bodies than traditional koi
  • Butterfly koi require the same care and have most of the same characteristics as regular koi

What are Butterfly Koi?

Butterfly Koi

Butterfly koi are not technically koi according to strict Japanese definitions of the word, but rather a cross between long-finned Indonesian carp and traditional koi (which are also in the carp family). For the casual koi keeper, though, they are koi in all the ways that count: size, longevity, behavior, coloring, diet and general appearance.

Where butterfly koi differ from regular koi are their fins. Unlike traditional koi, which have genes that tell their fins to stop growing at a certain point, butterfly koi fins keep getting longer throughout their lifetimes. The result is the long, flowing fins that some pond owners love. Butterfly koi's bodies also tend to be slightly more slender than traditional koi's, and their barbels - the whisker-type growths on their faces - grow slightly longer.

Keeping Butterfly Koi

Are you an experienced koi owner? Then you already know how to care for butterfly koi; their upkeep is almost identical. Feed your butterfly koi just as you would a regular koi, keep your water aerated and make sure they have plenty of shelter from the sun and predators. Butterfly koi are just as docile as other varieties, so feel free to place them in ponds with goldfish, catfish, orfes or other koi.

How big will a butterfly koi get?

Gold Butterfly KoiButterfly koi are skinnier than their short-finned cousins but grow to roughly the same length: usually about 12 to 15 inches. Some Japanese koi grow even longer, while jumbo varieties might grow as large as 3 feet long!

How long does a butterfly koi live?

Butterfly koi have about the same lifespan as traditional koi: up to 25-30 years in ideal conditions. Some koi keepers say butterfly varieties are slightly more hardy than other kinds because of their hybrid genes and close ties to wild carp.

Are there any differences between caring for a butterfly koi and a regular koi?

So what does all this mean for you, the casual pond owner who just wants to relax and enjoy some beautiful fish? Not much. The only additional precaution you need to take with your butterfly koi is to be extra gentle with those beautiful long fins. They can easily bend or tear, and the damage - although usually cosmetic - is often permanent.

Butterfly Koi: Where Did They Come From?

Here's what we know about the origin of butterfly koi: They started as a breed of long-finned carp, and breeders only started selling them commercially in the mid 20th century. Beyond that, the exact story of how these beautiful fish became staples of so many ponds is the subject of some debate.

While some sources say Japanese breeders started cultivating long-finned koi long before the fish made their way to the U.S., others say the breed originated with a company in New York in the early '80s. Those breeders took a chance on some long-finned feral carp from the waterways of Indonesia but quickly discovered that the fish was just plain ugly: gangly-finned with plain brown and gray coloring. Over the course of several generations, however, they selectively bred these new fish with prettier koi varieties to create the beautiful animals pond owners love today. The New York koi breeder's son, the story goes, noticed that these new fish looked like butterflies, and the term butterfly koi was born.

Butterfly koi are not universally popular. Some serious koi keepers consider them mutts because of their cross-breeding with feral long-finned carp, and many koi competitions exclude butterfly varieties because of inconsistencies in their size and appearance. Still, butterfly koi have grown popular in the United States over the past several decades among pond owners who care more about their look than their heritage.

Learn More

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