Koi Carp and Goldfish have a similar appearance — and in fact, the two are related — but they are actually different species of fish altogether. Once you know what to look for, the two are easy to tell apart as they have drastically different body shapes.

Goldfish were developed by selectively breeding a Prussian Carp for desirable color traits and they are now considered an entirely different species from the Carp, whereas Koi Carp are still considered a part of the Carp species. This is what makes the two fish so similar in appearance, but there are some important distinctions to be made between the two.

In this article, we’ll take an in-depth look at both species of fish to find out exactly what makes them so unique.divider1- goldfish

Visual Differences

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Goldfish are usually far smaller than Koi Carp and can be seen in a much wider variety of body, fin, and tail shapes as well as sizes. The most obvious visual difference between the two is the presence of barbs on the Koi Carp, a trait which the Goldfish is lacking. Another telling difference is in the fins: the Goldfish has a split tail fin, and detached dorsal fin, whereas the Koi Carp’s dorsal fin is attached all the way down its body. Koi also tend to have a far wider range of colors and patterns than Goldfish.goldfish divider

At a Glance

Koi Carp
  • Average length (adult): 24 – 36 inches
  • Average weight (adult): 20 – 35 pounds
  • Lifespan: 25-35 years
  • Habitat requirements: High
  • Colors: Red, white, black, blue, yellow
  • Average length (adult): 2 – 6 inches
  • Average weight (adult): 0.2 – 0.6 pounds
  • Lifespan: 10 – 15 years
  • Habitat requirements: Moderate
  • Colors: Orange, red, black, blue, grey, brown, yellow, white
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Koi Carp Overview


Koi Carp is a colored variety of the Amur Carp and have been kept for decorative purposes for centuries. Koi Carp are not a separate species from the common carp, and in fact, the word “Koi” is the Japanese and Chinese translation of the word “carp”. The breeding of these beautiful fish began in Japan in the early 19th century and they were bred and selected for their unique colors and patterns.

Koi Carp are highly intelligent creatures that cat be trained to get to know their owners, and even eat out of their hands! They are an important part of Asian culture and are revered as symbols of perseverance, endurance, and strength. Gold Koi Carp represents wealth and prosperity, blue serenity, and red positivity.


Breeding Koi Carp may seem relatively easy; simply place a male and female together in a pond and let nature run its course. However, it’s not quite that simple. The problem is that it’s rather difficult to correctly differentiate between a male and female Koi, thus making selecting the individuals for breeding a challenge. A basic method of telling the two apart is that males are more slender looking, while females have a rounder body, but only through experience will you learn to confidently tell them apart.

Around 3-6 years old is the ideal breeding age for Koi, although they can breed at older ages too, albeit less successfully. During breeding, Koi require a lot more energy and thus will need a lot more food, and you should feed them 3-4 times a day during this time. Lastly, like humans, Koi prefer privacy when breeding. The process may take some time, so give them ample space and privacy!


Koi Carp are fairly adaptable and hardy fish, but still require some specific conditions to stay healthy and happy. Their pond should maintain a temperature of between 74-86-degrees all year round, and so you’ll need a heating system during colder months. PH balance is also a vital factor, and needs to stay between 7.0 and 8.6 — anything below or above this may cause poor health or even death.


Water plants are also a great addition to their habitat, including water lilies, hyacinth, and duckweed, and small plants or trees to shade the Koi pond are great to keep them cool too. Koi fish need a lot of space to swim around and need roughly 250 gallons of water per adult to live happily. You can see why keeping Koi Carp can rapidly become expensive.

Health & Care

Koi fish eat a wide range of foods, from small insects to plants and algae, and will even enjoy an occasional piece of fruit as a treat. Store-bought Koi food is the best option as a staple, and they’ll need to be feed at least once a day. The amount a Koi eats varies widely depending on the season, and they’ll typically eat less during the winter months.

Koi Carp are fairly healthy animals if cared for properly and prone to very few diseases. Most of the diseases they tend to suffer from are usually easily treatable too, and so caring for a Koi is typically easy if their habitat and diet are properly maintained.

Suitable for:

Koi Carp need a lot of space, and so are ideally located outdoors in a large pond. This makes them better suited to owners that have the space in their yards to house them. These fish do not do well alone or living in small tanks, and so are not suited for small apartment living. They make a great addition to an outdoor environment in the home where they have plenty of space to swim, and plenty of shade.


Goldfish Overview


Goldfish are descendants of the Prussian Carp, and so have some shared history with the Koi Carp. That said, they are a wholly separate species and have only a small resemblance to their carp ancestors. Goldfish come in all shapes and sizes due to selective breeding and can vary widely in colors, fin styles, and eyes. Most commercial goldfish are suited to indoor living only as they are fairly sensitive, but there are some variations that do well in outdoor ponds too.


Goldfish breeding is fairly complicated and not a very easy task. Goldfish need specific temperature changes to induce breeding, as living in the wild they will usually breed in spring, so you’ll need a temperature-controlled tank to successfully breed them. Differentiating males and females can also be a challenge, and you’ll typically need to wait until they reach full maturity — about a year old — before you can sex them.


Goldfish require a lot of tank space to stay healthy and happy, about twice the amount of tropical fish and prefer warmer temperature water too. In the wild, they prefer slow-moving, calm water, and enjoy loads of aquatic plant life. They are fairly easy to look after, and a large tank filled with plants is ideal. Contrary to popular belief, a small fishbowl just won’t cut it!

We recommend a tank of at least 20-gallons per fish, and you’ll naturally need a larger tank if you plan on adding more fish. Goldfish produce a fair amount of waste as they are almost constantly eating, and so adequate filtration is essential. They need a PH of between 6.0-8.0 and prefer still water.


Health & Care

Goldfish have large appetites and are almost always on the lookout for food, but still, for the most part, Goldfish are largely overfed. Commercial Goldfish Flakes are ideal as their primary diet, preferably the floating kind, with the occasional treat of bloodworms or mosquito larvae. A Goldfish only needs to be fed once a day, preferably in the morning, and you should only feed them what they can eat in about 2 minutes and then remove the rest.

With a proper diet and well-maintained tank, a Goldfish can live for up to 15 years, and so they are generally a healthy pet. The biggest factor to look out for is stress, as this can often lead to illness and lack of appetite. Make sure their tank is clean, warm, and that the PH balance is good, plus keep them in a calm and serene environment to reduce stress.

Suitable for:

Goldfish are an ideal pet for owners that live in small homes or apartments that don’t have the space for an outdoor pond. They are fairly low maintenance and are generally healthy animals that live long lives, and so are a great choice for families with children.

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What Are The Differences?

Koi Carp and Goldfish are closely related, the Goldfish being developed form the Carp. They both come in a wide array of uniquely beautiful colors and both make fairly low-maintenance pets to have around the home. There are some distinct differences between these two closely related fish, however.

Koi Carps are far larger than Goldfish, with long, slim bodies as opposed to the Goldfish’s round, short body. Goldfish can be found in a larger variety of shapes and sizes, plus have more fin and tail shapes than Carps. The biggest visual difference is the Koi Carp’s barbs, a trait the Goldfish doesn’t share. Goldfish also have a split tail fin and detached dorsal fin and are found in fewer color variations than Carp.

Goldfish are a lot easier to look after than Koi Carp. They do not need as much space as they are physically far smaller, and so can easily be housed indoors. Koi Carp can reach up to 36-inches in length and need around 250 gallons of water per adult to stay happy and healthy, and so need a large outdoor pond to cater to their needs.

Featured image credit: Pixabay