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41 Facts About Goldfish That Will Surprise You

Nicole Cosgrove

Goldfish are the most popular pet in the world. Every year, over 480,000,000 are sold. Just to put that in perspective, that means there are more goldfish sold than dogs and cats combined. You may even have a goldfish yourself!

Even though goldfish are really popular, many people don’t know a lot about their scaly pets. In fact, most people believe myths and false information about these fish. There are probably a few things you believe about goldfish that are not true.

To find out some really interesting facts about goldfish, keep reading. In this article, we give 41 facts about goldfish that will surprise you. Let’s swim on into the facts now.

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Facts About Goldfish Anatomy

1. Goldfish have brains.

Many people do not think goldfish are very smart and assume that goldfish do not have brains. This is simply not true. All living animals have brains. Not to mention, goldfish are pretty smart, which we will learn more about in the goldfish intelligent section.

veiltail goldfish in a tank
Image Credit: Hans Braxmeier, Pixabay

2. Goldfish eyes can detect ultraviolet and infrared lights.

Human eyes have evolved to see combinations of red, yellow, and blue. Goldfish eyes are actually better at seeing colors. They have the ability to detect ultraviolet and infrared lights. This allows them to see combinations of four different colors, not just the three our eyes can pick up.

A goldfish’s ability to detect this extra color allows it to see movement and find food a bit easier. However, goldfish don’t actually have good eyesight. Because their eyes are on the side of their head, there is a blind spot in front of their face, and they cannot see very far.


3. Goldfish don’t have eyelids.

Goldfish do not have eyelids. Because of this fact, they cannot blink, and they do not close their eyes to sleep. It may be best to turn the lights off at night so that the goldfish’s sleep is not thrown off from the light.

goldfish close up
Image Credit: Narcis Ciocan, Pixabay

4. Goldfish taste with their lips.

Have you ever noticed that your goldfish pecks at things within its aquarium? It does this because it is wanting to taste everything around. Unlike us, goldfish do not have taste buds on their tongues. Instead, they have taste buds on their lips and on the inside and outside of the mouth.


5. Goldfish don’t have tongues.

Their taste buds are on their lips and mouth for a reason. Goldfish don’t have tongues. Instead, goldfish have a bump on the mouth floor, but it doesn’t move like your tongue does.

goldfish in a pond
Image Credit: Zichrini, Pixabay

6. Goldfish teeth are in the back of their throats.

If you look at your goldfish’s mouth, it looks as though it does not have teeth, but goldfish have flat teeth in the back of their mouth. These teeth are called pharyngeal teeth, and goldfish are not the only species to have them. These teeth are used to crunch and grind the food before it goes into their long intestine.


7. Goldfish don’t have stomachs.

A stomach is something that nearly every animal has, but not a goldfish. Most fish only have a long intestine that digests the food in different areas. This causes the food to move through the goldfish much faster than it would if the goldfish had a stomach.

lion head goldfish in an aquarium
Image Credit: Tina Designs, Pixabay

8. Goldfish scales tell you the age of the goldfish.

Just as you can tell the age of a tree by looking at the tree rings, you can tell the age of a goldfish by looking at the scales. Every year the goldfish is alive, it will develop rings on the scales. These rings are called circuli. Count how many rings are on the scales to figure out exactly how old your goldfish is. Although this may sound simple, you need a microscope.


9. Goldfish get their color from the sun.

Speaking of scales, goldfish get their color entirely from the sun or light. If you take the light source away from the fish, they will not be able to produce pigment, causing them to turn completely white. What is really interesting is the fact that there are countless color combinations found in goldfish. You will never find two goldfish with the same colorations and patterns.

two goldfish with different color pigments
Image Credit: Juan Carlos Palau Díaz, Pixabay

10. Some goldfish can be albino.

If you were to remove the light source from your goldfish and it turned white, it would not make the goldfish albino. Even though your goldfish would not be albino, there are albino goldfish out there. You can determine a white goldfish from an albino goldfish by looking at its eyes. Albino goldfish will have pink pupils, not black.


11. Goldfish scales are CLEAR.

This fact will probably shock you quite a bit, but goldfish scales are actually clear. The skin underneath their scales is what makes them have color. Goldfish scales are all clear, but they can be metallic, matte, or nacreous.

goldfish white scale
Image Credit: Juan Carlos Palau Díaz, Pixabay

12. Goldfish can detect changes in pressure.

The five human senses are sight, sound, smell, taste, and touch. Goldfish have all of these senses plus one more. They can detect changes in pressure, such as vibrations and currents. They are able to do this because of a lateral line, which is a tiny row of dots, that runs down their side.


13. Goldfish make noises through their noses.

Goldfish make sounds, even if you can’t hear them. Using special technology, researchers detected goldfish making noises through their noses. The noises were comparable to squeals or grunting, and they are most commonly heard during eating and fighting.

Goldfish eating fish food
Image Credit: Rabbitmindphoto, Shutterstock

14. Tapping on the tank will stress your goldfish out.

Even though you cannot see their ears, goldfish have internal ears, which are called otolith. It allows them to hear, though their sense of hearing is not as good as humans. Their ability to hear means that tapping on their tank will stress them out.


15. Your goldfish can probably smell better than you.

Goldfish have an impressively developed sense of smell that is often considered better than the ability of humans. They smell through the flaps above their mouth. These flaps are the fish equivalent to nostrils, or more technically called nares. Bad smells can actually make your goldfish feel dizzy.

goldfish eating
Image Credit: TD wt, Shutterstock

16. Goldfish grow to the size of its tank.

Goldfish will typically grow to be the size of its tank. If you have a small tank, it will be a small goldfish and probably die quickly. If you have a really large tank, the fish may grow to be huge. You need to change the water frequently. Goldfish produce a hormone responsible for regulating their growth. This hormone is released whenever the water is not changed frequently enough.


17. Their fins and scales can grow back.

If your goldfish has been injured, do not immediately panic. If you properly clean the goldfish’s tank, it should be able to grow back injured fins or scales. The only exception to this is if the fin has been completely shredded to the base.

Image Credit: Dia L., Pixabay

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Facts About Goldfish Reproduction

18. Males have white dots on their gill plates or fin rays.

If you look closely at a male goldfish, it will typically have white dots either on the gill plates or fin rays. These white dots are rough like sandpaper. Experts are not sure what these white spots are for, but many predict that they’re used for impressing females for mating.


19. Goldfish lay 1,000 eggs at a time.

A female goldfish will lay at least 1,000 eggs at a time. However, not all of these eggs will hatch. Some are never fertilized, whereas others are eaten before they are able to hatch. Because there are so many eggs at one time, goldfish can reproduce really quickly.

In fact, a couple of goldfish were released in a lake in Boulder, Colorado. It only took three years for the fish to completely overrun the lake. It wasn’t until herons ate the goldfish that the natural balance was restored.


20. Females don’t get “pregnant.”

Although female goldfish lay 1,000 eggs at a time, females cannot get pregnant. Female goldfish never have live young inside them. Instead, a female goldfish releases her eggs before they’re ever fertilized. The eggs stay outside the mother’s body until they hatch.


21. You can breed a koi with a goldfish, but their offspring will be infertile.

It is fully possible to breed a goldfish with a koi, but their offspring will be a mule, which is a fish that cannot reproduce. Black comet goldfish is just one example of a hybrid between goldfish and kois. You can see the koi heritage by looking at the small barbels on the goldfish’s mouth.

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Facts About Goldfish Food Habits

22. Goldfish will eat other fish.

Even though you feed your goldfish little pellets or flakes, goldfish will actually eat other fish, as long as it can fit in its mouth. In fact, goldfish will eat just about anything that fits in their mouth, including their babies and poop. This is why you should not keep goldfish in an aquarium with much smaller breeds.


23. Goldfish can and will eat itself to death.

Goldfish don’t have a stomach, making it difficult for them to know when they are full. This causes many goldfish to eat themselves to death since the goldfish’s purpose in life is to eat. Monitor how much you feed your goldfish during feeding time for this reason.

goldfish eating
Image Credit: oatpost, Shutterstock

24. Goldfish can live without food for up to 3 weeks.

Even though goldfish are constantly on the hunt for food, they can live for up to three weeks without any snacks. That’s because goldfish store fat for lean times. So, you don’t really have to hire a pet sitter whenever you go out of town to feed your goldfish.


25. You can feed your goldfish out of your hand.

Goldfish have the ability to recognize faces (more on this later), which allows them to know you are their food giver. This means that you can feed goldfish out of your hand if you are willing to be patient and train them not to be afraid of your hand.

You May Also Like: 10 Best Goldfish Foods of 2021 – Reviews & Top Picks

hand feeding goldfish
Image Credit: Peter Dakomd, Pixabay

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Facts About Goldfish Intelligence

26. Goldfish have a FIVE-MONTH memory.

One of the most common misconceptions about goldfish is that they only have a three-second memory. This is simply not true. Studies have suggested that goldfish actually have a memory of five months. Scientists from Israel discovered this by training goldfish to come to the sound of a dinner bell.


27. Your goldfish has a longer attention span than you.

Humans have an average attention span of eight seconds, but goldfish have an attention span of nine seconds on average. This means your goldfish is better at focusing than you are.

oranda goldfish
Image Credit: Rethinktwice, Pixabay

28. Goldfish can do tricks.

Goldfish are so smart that you can actually train them to do tricks. Using food as positive reinforcement, you can teach goldfish to do things like pushing a ball through a hoop or going through an obstacle course. There are other things you can teach them too!

You can even teach goldfish to chase laser pens. It is believed that goldfish chase laser pens as a response of their hunting instincts. You can even make an entire school of goldfish chase a single laser pen.


29. Your goldfish probably recognizes you.

Goldfish have the ability to recognize faces, shapes, colors, and sounds. This fact means that your goldfish probably recognizes you and knows you as its feeder.

goldfish eating in a pond
Image Credit: Corinna Behrens, Pixabay

30. Goldfish can recognize different music and composers.

Just like you can distinguish an Ariana Grande song from Metallica, it seems that goldfish can actually learn to recognize different music and composers. Japanese researchers trained goldfish to recognize music from Bach and Stravinsky. Half of the goldfish bit a red bead whenever Bach played, while the other half bit when Stravinsky played.

It should be mentioned that it took about 100 lessons for a goldfish to start recognizing the difference between the music. After the lessons, about 75% of the goldfish were picking the right composer consistently.


31. Goldfish get bored.

Wouldn’t you get bored if you lived your entire life inside a clear bowl? Goldfish too. Goldfish actually get really bored. To give your goldfish some amusement, put fibrous veggies inside the bowl for them to forage on throughout the day.

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Facts About Goldfish Legend, Lore, And Culture

32. Goldfish were a sign of friendship in Asia.

Before goldfish became really popular around the globe, goldfish were a sign of friendship in Asia. Giving a goldfish to someone else meant that you viewed them as a friend. Because of this practice, it was customary for husbands to gift their wife a goldfish for their first anniversary present.


33. Goldfish were once a sign of luxury and royalty.

Way back in China’s past, goldfish were so rare that only the royalty could afford them. This made goldfish a sign of luxury and royalty. The yellow goldfish were the favorite among royalty because yellow was the Imperial color. Yellow goldfish were so rare that they were actually banned from being owned by the peasants.

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Other Fun Facts

34. A school of goldfish is called a troubling.

Troublings are a little different from other schools of fish because there is no leader. Whenever one fish swims in a different direction, either the entire troubling follows, or the lone fish will swim back to the group.


35. President Grover Cleveland loved goldfish.

Many animals have called the White House home. For Grover Cleveland, his pet of choice was Japanese goldfish for the ponds. President Cleveland didn’t just have a couple fish, though. He had hundreds!


36. Goldfish have the most varieties than any other species.

To date, there are over 300 varieties of goldfish. All of these varieties make goldfish the number one species based on variety type alone. It has taken thousands of years for breeders to create this many varieties.


37. Goldfish are related to carp.

Through thousands of years of selective breeding, the goldfish descended from the carp. It may be helpful to think of the carp as the great, great grandfather of the goldfish.

goldfish veiltail
Image Credit: Pixabay

38. The largest goldfish was 18.7 inches long.

When kept in a small bowl, goldfish will stay small, but they can grow really big if taken care of properly. The largest goldfish was 18.7 inches long, which is the average size of a cat, not including the tail. Imagine keeping that big boy as a pet!


39. Goldfish can live to be 40 years old.

Most people have goldfish that die rather quickly. When taken care of properly, goldfish can live to be over 40 years old, making them the longest living domestic fish. Fish that do not live long die early because they were not taking care of properly.

lionhead goldfish
Image credit: Arunee Rodloy, Shutterstock

40. Goldfish can withstand a lot.

Part of the reason that goldfish can live so long is that they can withstand a lot. For example, they can live in temperatures as high as 100 degrees Fahrenheit, winter ice, or toxic water. Some goldfish have even been known to live a long life even in a fish bowl, which is typically considered a bad environment for goldfish.


41. Goldfish can hibernate.

If you keep your goldfish outside during the winter, it will actually hibernate. This hibernation involves the goldfish slowing down its heart rate and stopping eating before going to sleep. After the winter ends, the goldfish will be ready to spawn.

colorful goldfish in a pond
Image Credit: Ravi Mohan, Pixabay

Featured Image Credit: dien, Shutterstock

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Nicole Cosgrove

Nicole is the proud mom of Baby, a Burmese cat and Rosa, a New Zealand Huntaway. A Canadian expat, Nicole now lives on a lush forest property with her Kiwi husband in New Zealand. She has a strong love for all animals of all shapes and sizes (and particularly loves a good interspecies friendship) and wants to share her animal knowledge and other experts' knowledge with pet lovers across the globe.