What’s the Difference between Koi and a Goldfish? 9 Things You Must Know

Some people love to have aquariums and ponds in their homes. It adds to the aesthetic appeal of their living space, with colorful fish swimming around in water. However, some folks are unsure which type of fish would suit them best.

Koi and goldfish are among the top choices for homeowners. However, people often get confused between them. If you also ask yourself, “What’s the difference between Koi and a goldfish?” we can help you answer this question.

Even if they look the same to you, both of them are poles apart. Koi and goldfish have different habitat needs, and it may be hard to keep them together in the same aquarium. Let’s go over some key differences between koi and a goldfish to determine which one would be best for you!

Here are 9 Differences between Koi and a Goldfish

1. Origin

Koi and goldfish origin stories are more interesting than many other species of the sea. They are hybrids bred from the efforts that started in the Tang Dynasty of China.

Goldfish are the offspring of Prussian carp, a food fish with olive green pigmentation. Since they lived in small ponds, the coloration was not interesting enough for onlookers as it blended with the background. However, some pond-keepers noticed a few fishes with gold and orange coloration.

These two fishes were moved to much smaller ponds and raised as pets. They eventually started mating and producing multi-colored fishes, known as goldfish today.

Koi fish lineage is a bit more complicated than the simple story of goldfish. At first, people assumed that koi are bred from common carp based on the early Jin Dynasty records. However, the 1820s selective breeding of Amur carp by Japanese produced Nishikigoi fish, known as koi fish.

2. Difference in Color Pattern

Goldfish have a range of color patterns. They have orange, black, red, blue, grey, yellow, white, and brown shades. They can also be differentiated based on their size; goldfish look different with their 2-6 inches length.

On the other hand, koi come in a broader range of colors. They have exotic and classic golden pigmentation, but the typical koi are red, blue, white, and black. Koi are 24-36 inches long, so their appearance is significant differences between koi and a goldfish.

goldfish and koi colors

3. They Both Have Fins But…

Fins can also help you distinguish goldfish from koi. Goldfish fins are unique with a single caudal or anal fin. Single-tailed goldfish have caudal ones, and fan-tailed have anal fins.

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You are most likely to find goldfish with single tails, as they are common for aquariums. The ones with fantails and double caudal and anal fins are fancy goldfish.

Koi fins are not that exotic compared to goldfish. If you look at a koi fish, you’ll notice that the fin shapes are pretty basic, like carp fins. However, there is a fancy version of this species, butterfly koi.

They have flowing fins with various color patterns. Some people are koi purists or enthusiasts, so they do not consider butterfly koi legitimate.

4. How Long Do They Live?

The lifespan of goldfish and koi vary as much as their color patterns. Goldfish have different lifecycles based on their environment and type. Moreover, water quality, feeding, and aquarium care play a vital role in their living status. Fancy goldfish can live for fifteen years, and a common goldfish will survive 43 years in a large bowl.

Koi’s lifespan is much more than a goldfish’s. In fact, there was a koi in Japan who lived for 226 years. The fish was called Hanako, a ‘flower girl,’ born in 1751. She died in July 1977. However, this has never happened since. The average lifespan is 50 years for koi. They can live longer if their habitat is suitable.

5. Aquarium Life for Koi and Goldfish

For goldfish, aquariums are their home away from home! They can easily thrive in a water body enclosed in glass. However, the space cannot be too small. Tanks or bowls that do not allow goldfish to swim are not the best places for their growth.

Also, keeping the fancy ones separate from tropical goldfish is essential to manage the food chain. That’s because fancy goldfish are slow swimmers.

Keeping koi in a small enclosed environment is close to impossible. They are much larger than goldfish and require at least 100 gallons of water in a tank to swim freely. If you do not have a large aquarium, you should avoid getting a koi. However, if you have an outdoor pond at home, that’s the best place for koi to grow.

difference between koi and a goldfish

6. What Do They Like to Eat?

One of the major differences between koi and a goldfish is their eating preferences. It can determine which fish you would be able to afford easily. Goldfish like to eat works, fish eggs, crustaceans, and bits of plant matter. They have small mouths, so they can’t overeat live food. However, they are omnivores through and through!

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Goldfish teeth are pharyngeal, so it’s easier for them to grind their food before swallowing. They do not have stomachs, so the food directly passes on to the intestines. You can feed them small pelleted food, frozen or live shrimp and worms.

Koi fish have larger mouths than goldfish, so they can dig into the mud and find their food. They have similar teeth and digestive systems as the goldfish. There is no stomach, so the food goes directly to the intestines.

They are omnivores with a palate for insects, worms, crustaceans, fish eggs, and water plants. They also eat small fish if they get closer to the koi’s mouth.

7. Plants vs. Koi and Goldfish

You know that koi and goldfish are both omnivores, but they have different preferences for plant-based foods. Goldfish would leave the plants alone if they find it in their habitat. You can use plastic plants to avoid the crucifixion of live plants by goldfish. They live to uproot them.

Koi love to eat plants. They have larger mouths and sharper teeth to grind them. They can easily consume aquatic pond plants that are smaller in size. Koi will eat lily leaves and floating plants closer to their mouths. They can also dig the soil using their mouths, so uprooting plants for consumption is natural.

8. How Do They Like to Be Looked After?

Managing a habitat for pet goldfish or koi is vital for their survival. If the pond or aquarium is not sterile with excellent water quality, the fish won’t survive.

Goldfish treatment is easier than koi because there is less water in their bowl or tank. If you find that your goldfish is sick, you can change the water and add an adequate amount of medication for treatment.

Koi fish are challenging to take care of. Outdoor ponds are difficult to clean, which becomes an issue for sick koi and goldfish. The entire pond will have to be treated if there is no temporary space to keep the koi. It is extremely costly to treat a pond.

medical treatment for koi and goldfish

9. What If They Get Sicker?

Goldfish will not get sick as long as their living situation is ideal. If they do get sick, you can easily remove them from the aquarium using a regular net and cradle the fish in your hands without trouble. Fancy goldfish will not move much in your hands, but tropical ones have longer bodies, so they flop around a lot.

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Koi, on the other hand, can survive extreme weather conditions. Still, they can get sick and develop conditions that cease their growth. Common koi diseases include anchor worms, Dropsy, and Aeromonas. Bacteria and viruses can cause these diseases, and isolation of koi is the only way to treat it.

However, it would help to prepare yourself for challenging koi transportation because they will flop around a lot in your hands.

Koi vs. Goldfish – Which One to Choose for Your Pond

This video talks about the main pros and cons of keeping koi and goldfish in your pond! If you want to know which type of fish would suit you best, you can watch their pond life here.


We hope this article has answered your question about what’s the difference between koi and goldfish. Both species make adorable pets to have. You can choose to have one or both of them based on how well you are able to care for them. If you have a bigger aquarium and can feed the fish properly, you can buy a koi.

However, goldfish would be a great choice if you want something easier to manage. They can live happily in small aquariums and won’t ask for too much food! Whichever you decide to get, we hope you can enjoy the experience of living with these beautiful creatures!

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