10 Differences Between Koi And Goldfish | Aquascape Addiction

10 Differences Between Koi And Goldfish

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Here are the main 10 differences between Koi and Goldfish, it's actually a lot more than a matter of color and size. Here is a detailed summary of the two.

10 Differences Between Koi And Goldfish

Goldfish and Koi are both pretty common pets to have at home, with goldfish being the far more common of the two. Now, you have probably heard of both goldfish and koi, but may not know what the differences are.

The difference between Koi and goldfish is not just their size and color, but so much more. Let’s take a look at all of the main differences between goldfish and Koi right now.

Koi VS Goldfish – 10 Main Differences

Let’s now take a look at the main difference between Koi and goldfish. There are quite a few, so get ready!

Koi Fish Comparison

1. Origins

Both Koi and Goldfish originate from China, specifically during the Tsang dynasty, all the way back in the early 600’s.

Koi lineage is actually very hard to prove or confirm, but it is thought that the Koi is a result of the selective breeding of the colored Amur carp during the early 1800s.

These fish were then called Nishikigoi, what is now known as the Koi fish. However, what is now known as the common Goldfish is the result of the Prussian Carp, which at first had really drab colors, but was then bred selectively to create what we now know as the goldfish.

The common goldfish is a result of part selective breeding and part natural breeding.

2. Appearance

The next main difference is their appearance. In terms of size, Koi can grow up to 3 feet in length, whereas most goldfish are going to top out at 10 or 12 inches in length at the very most.

Next, Koi tend to have a very elongated body with mouths that face downward for easy feeding and foraging, whereas your average goldfish is not quite as elongated, or in other words, a bit rounder, and their mouths don’t face downwards either.

Koi also have little beards known as barbels, two pairs on each side of the mouth, which normal goldfish do not. comet, shubunkin and common goldfish do look a bit similar to Koi, but will never grow as large as Koi.

3. Colors And Patterns

Another main difference between Koi and goldfish has to do with their colors and patterns. Normal goldfish tend not to have very complex or diverse color schemes.

Goldfish generally have black, red, and yellow pigments, with some gray, blue, and brown pigments making rare appearances.

On the other hand, Koi have been bred to have far richer and more diverse colors and patterns. The main colors you will see Koi come in include various combinations of white, black, blue, red, yellow, and cream.

There are over 23 different types of Koi color combinations and patterns, and they can include any of the above colors.

4. Fin Shape & Type

Goldfish Comparison

When it comes to Koi, they have very basic fins, just like a common carp. There is a variety of Koi known as the Butterfly Koi, which has longer flowing fins, but these are often not considered to be true Koi fish.

There are a couple of long finned Koi varieties like this, but generally speaking, they usually all have very basic finds like common carp fish.

Goldfish on the other hand feature several different fin and tail types. There are single tailed goldfish and fan tailed goldfish, which have a single caudal fin and anal fin.

There are goldfish species such as the Shubunkin and Comet goldfish, which have somewhat deeper and longer tails than common goldfish.

There are then fancy goldfish such as the Orandas and Pearscale goldfish, which have double fin tails. There are also a select few which have triple or quadruple lobed tails, such as the Japanese Ryukin.

5. Age

The simple fact of the matter is that Koi do get much older than goldfish. Your average Koi can live for between 30 to 50 years, with it not being uncommon to grow to 50 years old.

On the other hand, while the record age for the common goldfish is 43 years old, on average, in a home aquarium, you can expect a common goldfish to live to between 5 and 10 years of age, with some maybe reaching 12 or even 15 years old if properly cared for.

6. Feeding

So, both goldfish and Koi feature pharyngeal teeth, which are teeth located in the throat, which are used to grind food. Both goldfish and Koi also do not have stomachs, as food passes from the mouth straight to the intestines.

Now, the main difference here, besides the fact that Koi mouths face downwards, whereas goldfish mouths do not, is that goldfish just have much smaller mouths than Koi, which therefore limits the size of food that they can eat.

Goldfish do fine with flakes and pellets, as well as small shrimp, worms, and other such foods. On the other hand, Koi will eat all of these, and thanks to their larger mouths, will also eat smaller fish and crustaceans.

Of course, due to their size, Koi also eat much larger amounts of food than goldfish.

7. Keeping Them

Another main difference is that you can easily keep a goldfish in a home indoor aquarium. Normal goldfish, depending on the exact type of goldfish, will do fine in aquariums ranging from 10 to 40 gallons.

However, because Koi grow much larger, each Koi needs at least 100 gallons of tank space, if not 125 gallons.

Therefore, unless you have a massive indoor aquarium, Koi can really only be kept in ponds. Koi really cannot be kept in normal size aquariums like goldfish.

8. Living with Plants

Something else to keep in mind here is that Koi will try to eat virtually any and all plants they come into contact with.

On the other hand, in an aquarium, for the most part, goldfish tend to leave plants alone, making it much easier to keep goldfish with plants.

That said, goldfish like to dig and uproot plants, which makes some people use plastic plants to prevent this from occurring. However, Koi fish also do this.

9. Handling & Treating Disease

The other thing that should be noted here is that due to their large size, Koi are of course much heavier and tougher to handle than a small goldfish.

On that same note, because Koi are large and their ponds are big too, if a Koi gets sick or disease takes hold, treating a large Koi pond for any disease is much more difficult than treating a small goldfish tank.

10. Cost

When it comes to cost, there is a big price gap between buying koi and goldfish. Koi carp can get very expensive, the cost vastly varies depending on the size and color of the carp.

The price range can vary from a broad range of $10 to several thousand dollars (even hundreds of thousands or millions on dollars in some rare cases) depending on the size, rarity and color variation.

Goldfish on the other hand are certainly more cost-friendly with many costing below $10, again this can vary depending on the type but they are certainly much cheaper out of the two.

Commonly Asked Questions

Are Koi & Goldfish the same Species?

As mentioned in the first difference between these two, no, Koi and goldfish are not the same species.

Goldfish were developed through the selective breeding of Prussian Carp, whereas the Koi was created through the selective breeding of the colored Amur carp.

Can Koi & Goldfish Live in the same Tank?

This does depend on the specific fish in question, but generally speaking, yes, you can keep Koi and goldfish in the same tank.

Now, if you plan on keeping them together, the goldfish will have to be fairly large, at least 8 inches in length.

This is because Koi will eat smaller fish, especially anything under 3 or 4 inches in length. If you keep these two fish together, they should be relatively similar in size.

Do Koi Attack Goldfish?

So, this does somewhat depend on the temperament of the Koi, but generally speaking, no, Koi will not attack goldfish.

Once again, if the goldfish is a baby or a small juvenile, a Koi may attempt to eat it, but Koi usually will not bother an adult size common goldfish.


The bottom line is that while Koi and goldfish may look a bit similar, they are in fact totally different fish. Common goldfish have more fin types, but Koi have more color types, and of course, Koi are much larger and hungrier fish.

If you fancy having a pond, then the Koi is a good option, but if you just want a normal indoor aquarium, it’s the goldfish you will want to go for.