Goldfish and koi carp whilst related are actually very different species.

Koi carp were first developed and bred in Japan in the 1820’s in fact they are a domesticated version of the common carp which were bred for their highly unusual and bright colours and patterns.

Left alone in the wild, even the brightest and most visually impressive koi carp will interbreed with common carp, and revert to the standard common carp color palette and appearance within just a few generations.

The background of the goldfish goes back much further as it was developed in China over a thousand years ago, by selective breeding of the Prussian carp to develop the attractive colors and patterns that modern goldfish display.

Goldfish were later introduced to Japan, home of the koi carp, in the 16th century, then spread to Europe in the 17th century.

So what are the physical differences between the two?

The main differences between the two types of fish are:

• Goldfish are generally smaller than koi when adult.
• Goldfish can be seen in a much greater variety of body, fin and tail shapes than koi.
• Koi tend to have a greater range of color and pattern combinations than goldfish.
• Koi have clearly visible barbels near their mouths, which are missing from goldfish.
• Goldfish have a split caudal fin, while on koi, the caudal fin is joined.
• The dorsal fin of the goldfish is detached and free at the back, while on the koi, it is attached along the whole of its length.
• Koi are generally much longer lived than goldfish and while the two can interbreed, the resulting offspring are always sterile.

To read more visit the Your Koi Pond website