Fin-tastic Facts About The X-Ray Tetra For Kids

Enjoy reading some X-Ray Tetra facts on our page!

Thinking of which fish to add to your little fish tank? We might know the answer, and we think it is the beautiful x-ray tetra. This fish is also known as the water goldfinch, the golden pristella tetra as well as the x-ray fish. Why x-ray though, you may wonder? Well, these pretty fish have almost translucent skin and because of this, you can clearly see the insides of the fish, like an x-ray, you can see the bones, the organs, right before your eyes!

These schooling fish are found in abundance at the coastal waters of the Amazon and Orinoco in South America. The scientific name of this species is Pristella maxillaris. They prefer living in waters with pH values ranging between 6.0 to 7.0. The tetras are perfect for your home fish tanks and aquariums, swimming in large groups and enchanting the ones who see them. They are also pretty peaceful and wouldn’t mind other species of fish sharing the space with them.

Fascinated by knowing such amazing facts about the tetras? You might also enjoy reading our pages on the Toadfish and the cichlid.

X-Ray Tetra

Fact File

What do they prey on?

Insects, small crustaceans, worms, planktonic animals

What do they eat?


Average litter size?

300 – 400

How much do they weigh?


How long are they?

1.6-1.9 in (3.2-5 cm)

How tall are they?

1 in (2.54 cm)

What do they look like?

Transparent body; white, black, yellow striped fins

Skin Type


What are their main threats?

Water pollution, larger aquatic animals

What is their conservation status?

Not Listed

Where you'll find them

Brackish, acidic, alkaline waters


South America





Scientific Name

Pristella maxillaris





X-Ray Tetra Interesting Facts

What type of animal is an X-Ray Tetra?

The x-ray tetra, also known as the x-ray fish, is a type of fish.

What class of animal does an X-Ray Tetra belong to?

The x-ray tetra falls in the category of fish, under the Actinopterygii class.

How many X-Ray Tetras are there in the world?

We are not aware of the exact number, however, there is no need to worry because the x-ray fish is found in abundance in the oceans!

Where does an X-Ray Tetra live?

You will find this fish mainly in freshwater streams and tributaries during the dry days. However, it chooses the water bodies of savannahs during the wet season, which helps them to breed effectively.

What is an X-Ray Tetra's habitat?

The water goldfinch is found in water bodies that are both acidic as well as alkaline. They are also tolerant of water bodies that are slightly brackish.

Who do X-Ray Tetras live with?

You can classify the tetra as a schooling fish that always chooses to swim along with its fellow mates. You will find them in large shoals if you go for a deep-sea dive!

How long does an X-Ray Tetra live?

The average lifetime of this little animal is between two and five years.

How do they reproduce?

At the dawn of the rainy season, this freshwater fish swims to the flooded regions of savannahs to begin breeding, as there is more water to breed as well as enough food for all. The female tetra lays 300-400 little eggs, which are scattered everywhere in the water and vegetation. Thanks to their golden translucent skin, you can see the little eggs within her as well. About 24 hours later, the little fry hatch from the eggs, and in a few days' time, they are ready to zoom past each other and begin swimming. The beautiful fish matures when they are around five to eight months old.

What is their conservation status?

Their current conservation status according to the IUCN Red List is of Least Concern.

X-Ray Tetra Fun Facts

What do X-Ray Tetras look like?

The x-ray tetra is a beautiful little fish.

The x-ray tetra is also popular by its other name, the golden pristella tetra. This name comes due to the light golden tint on its translucent body. Their almost transparent body acts as a good camouflage for them against all predators, and these little ones are difficult to spot in densely vegetated parts of the water. The internal bone structure of the tetra is called the ‘Weberian apparatus’. This structure helps the fish in picking up the waves of sound underwater, and transmitting it down its vertebrae, thus improving its hearing. This little fish grows up to 1.9in, with the females being slightly bigger than the males. The dorsal and anal fins of the x-ray fish are bright yellow, white, and black striped.  Their tail fins have a soft pink to red hue. However, when the little babies hatch from their eggs, they are considerably paler and have a dull white shade of skin.

How cute are they?

We think this little schooling fish is absolutely cute! They are small, colorful, and totally peaceful.

How do they communicate?

Most fish make three different sounds for communicating, a purr, a pop, and a crock. These sounds cannot be heard by humans.  Usually, the sounds are produced by their swim bladder. Attached to this bladder is the sonic muscle, which contracts and then relaxes to pass the sound waves. Additionally, when they grit their teeth or hit their bones against each other, they can pass the sound to other fish.

How big is an X-Ray Tetra?

Tetras are actually really small, their average length is only the diameter of a golf ball!

How fast can an X-Ray Tetra swim?

There is no known information regarding how fast tetras can swim, but, interestingly, since these are schooling fishes, they all prefer swimming in coordination in the same direction while maintaining the same speed. If the shoal members do not follow this, the 'oddity effect' comes into play. As per this effect, any fish standing out from its shoal in terms of appearance or movement is more targeted by potential predators.

How much does an X-Ray Tetra weigh?

While there is no definitive answer to this, they are tiny fish and surely do not weigh very much!

What are their male and female names of the species?

There are no distinct names for male or female x-ray tetra fish.

What would you call a baby X-Ray Tetra?

The x-ray tetra babies are called 'fry'.

What do they eat?

The water goldfinch fish feeds on insects, small crustaceans, worms, and aquatic plants. The little tetra fry feeds on insect larvae.

Are they dangerous?

No, they are not dangerous at all.

Would they make a good pet?

Yes, it would be fun to have this translucent fish as your pet in a fish tank.

Did you know...

This freshwater fish has really sharp sense of hearing.  

Usually, the female tetras have a larger body than the male tetras, and that will help you distinguish between the two genders.

A group of x-ray tetra fish is called a school.

The main dangers they face are from predators like frogs, bigger fish, and birds. Water pollution is also a big problem for the x-ray tetra's habitat. They are mainly found in South America, around the Amazon coastal waters of Guyana, Venezuela, and Brazil. The tetras swim together in large groups between the middle of the water and the ocean floor.

This species is calm as a large group, however, in the presence of large predators or if the school size is small, the tetras get hyper and fidgety.

The Weberian apparatus of these animals consists of two sections. One section is known as Weberian ossicles, or the pars auditum, which is the movable part. The other portion is the supporting portion, known as pars sustentaculum.

Another interesting fact is that these little tetras are absolutely diet conscious. They make sure that there is a little of everything in all that they eat!

Thinking about adding them to your home aquarium? The little adorable tetras are absolutely perfect for your home tanks. They eat almost every fish food. They are well suited in waters having a pH value ranging between 6 and 8, and with temperatures between 22-28 °C. As they are one of the species that practice shoaling, it is recommended to keep them in a small group of at least six tetras in your tank. Though these fish have a lifespan of between three and five years, they tend to live longer in home tanks and aquariums, sometimes up to eight years!

Do people eat the X-Ray Tetra Fish?

No, these little tetras are not eaten by people.

What unique physical features does the X-Ray Tetra have?

What makes this tetra species unique is its transparent skin, something which you might not usually find in sharks, mackerel, or even kingfishes. Additionally, the scales on its body give a soft golden hue, making this fish look even more beautiful. The multiple bee-like stripes on its fins also make this tetra species different from the others.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other fish including the hammerhead shark and the Pacific salmon.

You can even occupy yourself at home by drawing one of our x-ray tetra coloring pages.



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