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Koi vs Goldfish: Why are They so Similar?

Koi vs Goldfish: Why are They so Similar?

When you compare koi to goldfish many people have a hard time telling them apart, and there is a reason for this mix up. Both koi fish and goldfish are decedents of carp so they are actually distant relatives. The goldfish is far older than koi fish. Goldfish were developed in China over 1,000 years ago while koi fish have only graced our ponds since the 1820's. Koi and goldfish show there similarities and differences in their color, body shape, and lifespan.

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Koi vs. Goldfish: Coloring

When it comes to coloring koi and goldfish are quite similar. Both these types of fish display orange, red, black, white, and yellow colors, they even both display combinations of those colores. However, koi fish display a greater variation in their coloring than goldfish do. Koi fish can be orange, red, black, white, yellow, or blue with many having metallic versions. The similarity is likely because of their shared ancestor, the carp, but because koi breeders desired more colorful fish more were developed while breeders of goldfish focused on createing their desired body type. 

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Koi vs. Goldfish: Body Shape

The biggest difference between koi fish and goldfish is their body shape. Goldfish have a variety of body shapes depending on the type of goldfish, but they are usually wider and egg shaped. Koi fish on the other hand are narrow and shaped like a torpedo no matter which type of koi you observe. Goldfish have split tail and dorsal fins while a koi's are connected. Some goldfish also have bulging eyes while no type of koi fish has that trait. The most telling difference between these to fish however is their size differences. the average koi fish grows to be  twenty-two to twenty-five inches long, but can grow to be over four feel long. Goldfish usually only grow to around four inches long but may grow to be around one foot if given enough space. This dramatically changes body shape likely greatly decreased the goldfish's lifespan.

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Koi vs. Goldfish: Lifespan

The lifespan of koi fish and goldfish is very different. Even though both koi fish and goldfish reach maturity when they are two to three years old the number of years they live after that varies dramatically. The average lifespan of a goldfish is five to ten years with the oldest recorded goldfish living to be forty-three years old. The average lifespan of koi fish is twenty-five to thirty-five years, more than doubling the goldfish's life expectancy, and the oldest known koi fish lived to be an impressive 226 years old.

Even though koi and goldfish share a common ancestor they were breed to be very different, however they have held onto some common traits. Koi and goldfish have similar coloring, but their body shape and lifespan are very different.

Were you as surprised as I was to find out goldfish are related to carp? Do you own any goldfish? Do you keep your koi fish and goldfish together? We would love to hear from you in the comments below!

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