What are 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.