When you look at the beautiful koi fish we have come to love it’s hard to imagine that these graceful fish actually descended from the common carp, and fairly recently too! Because of all the amazing changes the common carp has gone through there are now many differences between koi and carp. Most of these differences can be seen in the coloration, body shape, size, fins, and scales of the fish.

Koi vs. Carp: Coloration

The most obvious and most important difference between koi fish and the common carp is their coloration. Koi fish come in a whole spectrum of colors and patterns. Some of the colors common for koi fish are red, yellow, orange, black, blue, and white. The common carp on the other hand is almost always a dark brown or golden brown color which fades into a lighter hue near the fins and belly.

Koi vs. Carp: Body Shape

The body shape of the koi is very different from the common carp. The common carps body is more compressed and taller than the koi fish with much of its growth being in the midsection while the koi fish tends to grow longer. Selective breeding has lead to the perfect torpedo-like shape the koi has taken on with their midsection being thick and leading to a narrower head and tail.

Koi vs. Carp: Size

When compared to the common carp the koi fish tends to be larger with their average size being twenty-four the twenty-eight inches long while carp average fifteen to twenty-seven inches long. However carp regularly reach larger sizes than koi fish with the largest carp ever caught weighing in at a whooping 105 pounds compared to Big Girl (the world's largest koi) who is slightly smaller at ninety-one pounds. Those are some big fish!

Koi vs. Carp: Fins

One of the strangest differences between koi and carp can be found in their fins. The common carp has a separated spine in their fins with an elongated dorsal fin. As koi developed they lost these spines allowing for they beautiful flowing fins we see in the Butterfly koi.

Koi vs. Carp: Scales

The final big difference between the common carp and koi fish lay in their scales. While both carp and koi can lack scales altogether (these fish are called leather koi/carp) when they do have scales a koi fish’s scales are smaller, more regular, and more curved than the common carp’s scales.

Because of all these differences koi fish struggle to survive in the wild. The bright colors which make them beautiful make them easy prey, their lovely flowing fins make them weaker swimmers, and their smaller curved scales don’t protect them as well as a carps large scales. So the real difference between koi and carp is their habitat - carp are very hardy fish found across the world while koi thrive in carefully crafted ponds made to display their beauty.

Who would have thought so much change could happen in a few hundred years? What do you think was the most interesting difference? Let us know in the comments below!