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10 Facts About Goldfish You Need to Know

Last Reviewed and Updated on November 2, 2022

One of the most popular pet fish, the goldfish, is a pretty impressive animal. Read through these facts about goldfish and learn a bit more about them, from debunking a popular myth to the fact they can change colors under certain conditions.

1. Goldfish were selectively bred

One of the most interesting facts about goldfish is that they aren’t a naturally occurring breed. Asian carp, a fish that is typically gray, has been bred for thousands of years primarily for food. Some species of Asian carp occasionally had red, yellow, or orange color mutations, and people began to selectively breed the fish that had these specific mutations.

2. They don’t grow to their full potential size in an aquarium

When a goldfish is kept in an aquarium, it will typically grow up to about 2 inches / 5 cm long. If they are kept in or moved to a bigger fish tank, they will grow more, but usually won’t grow more than 6 inches / 15 centimeters in length. In the wild or larger ponds, they can grow twice that size.

3. Some breeds of goldfish can no longer breed naturally

Goldfish have been bred into many shapes, colors, and sizes, and some exotic specimens are paying the price. Due to their body shapes, some species can’t be bred naturally and can only be bred artificially with a method called “hand stripping.”

4. They can recognize individual humans

They will get used to people who feed them and pose no threat. When an unknown person approaches them, they may show fear.

5. Goldfish have a relatively good memory

A popular myth about goldfish having a three-second memory is just a myth. The memory span of a goldfish has been well studied for decades, and the consensus is their memory is pretty good, ranging from weeks to years.

6. If left in the dark for too long, they will gradually become gray

This isn’t something you should do, though. If goldfish are in the dark for too long, they will gradually lose their gold color, slowly becoming gray. The pigment responsible for their signature colors responds to light.

7. Goldfish don’t have stomachs

Instead of a stomach, their intestines break down the food and absorb the nutrients a goldfish needs.

8. They can hibernate

When the temperatures drop, a goldfish will enter a semi-dormant state called torpor (similar to hibernation but not exactly the same). The temperature of the water controls the metabolism of the goldfish.

9. There are over 300 breeds of goldfish

Celestial eye goldfish

There are over 300 different breeds of goldfish, each one unique in its own way – be it shape, size, or color variation.

10. They can survive out of water for an hour or more

These fish can be pretty hardy. If they manage to get out of the water and there is still some water on their body, they can survive for quite a while. That said, if you are a goldfish owner and you find your goldfish jumping out of the tank, the tank is either too small, or the goldfish has health issues that should be addressed.

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