News
SpeciesScientists Discover Mysterious New Fish in the Red Sea – and Have Never Seen It AgainOceanEye to eye with Britain's hidden sharks at SharkAdemy - OceanographicRiversIn October, biologists surveying a New York harbor for invasive fish pulled up a bright yellow one. It wasn't an invasive species at allOceanShedd Aquarium Sends Shark Eggs to Bolster Wild PopulationsSpeciesA rare fish has been found in Lake Ontario, North America, whose entire body is golden. It is a nati..OceanThe Great Sea Reef Is Fiji’s Wildest Dive, and a New Frontier for ConservationOceanEckerd College professor contributes to designating Biscayne Bay an Important Shark and Ray AreaSpeciesRio Verde Grande Survey Identifies Fifty-Three Fish Species Facing Flow ReductionsFisheriesAdams River Salmon Run in Thompson-NicolaIndiaHilsa production dropped 26% in five years, fisheries minister tells parliamentSpeciesScientists Discover Mysterious New Fish in the Red Sea – and Have Never Seen It AgainOceanEye to eye with Britain's hidden sharks at SharkAdemy - OceanographicRiversIn October, biologists surveying a New York harbor for invasive fish pulled up a bright yellow one. It wasn't an invasive species at allOceanShedd Aquarium Sends Shark Eggs to Bolster Wild PopulationsSpeciesA rare fish has been found in Lake Ontario, North America, whose entire body is golden. It is a nati..OceanThe Great Sea Reef Is Fiji’s Wildest Dive, and a New Frontier for ConservationOceanEckerd College professor contributes to designating Biscayne Bay an Important Shark and Ray AreaSpeciesRio Verde Grande Survey Identifies Fifty-Three Fish Species Facing Flow ReductionsFisheriesAdams River Salmon Run in Thompson-NicolaIndiaHilsa production dropped 26% in five years, fisheries minister tells parliament
EveryFish
Description: Closeup of a Pristella maxillaris, studio picture.

X-ray tetra

Small translucent South American freshwater fish popular in home aquariums.

Photo: Richard Bartz, Munich Makro Freak, CC BY-SA 2.5, via Wikimedia Commons

The X-ray tetra is a tiny ray-finned fish native to South America. It gained fame for its see-through skin and is widely kept by hobbyists due to its resilience.

Share on WhatsApp

  • Maximum length reaches 4.5 cm
  • Body skin is transparent revealing spine
  • Native to Amazon and Orinoco basins
  • Captive bred mainly in Eastern Europe
  • Considered ideal for beginner aquarists

What it is

This species belongs to the family Acestrorhamphidae within the order Characiformes. Adults reach a maximum length of 4.5 centimetres. The body shape is streamlined and fusiform. Skin transparency allows observers to view internal organs and the vertebral column directly. Scales display a yellowish-silver hue with golden tones. The caudal fin exhibits red colouration. Dorsal and anal fins feature black, yellow, and white spots. A distinct humeral spot matches the pupil size. The adipose fin remains clear.

Where it lives

Populations inhabit South American river systems. Records exist from the Amazon and Orinoco basins across Brazil and Venezuela. Coastal streams in the Guianas also host these fish. Habitats consist of slow currents or stagnant water bodies. Dense aquatic vegetation provides cover. These conditions support their natural lifestyle away from fast-flowing torrents.

How it lives

Information regarding specific dietary preferences remains absent from available records. Predators are not identified in the provided text. Schooling habits are not explicitly described. Movement occurs through vegetated zones in calm waters. No migration data is present.

Breeding and life cycle

Details concerning spawning rituals are missing. Juvenile growth rates are unknown. Reproductive timing cannot be determined from the current information. Captive breeding occurs extensively in Eastern Europe for commercial supply.

X-ray tetra
A drawing made by EveryFish from what this page says. It is a diagram, not a picture of the real fish.

Fish and people

Aquarium enthusiasts value this species highly. Breeders consider it hardy and simple to maintain. Beginners often select it as an introductory pet. Commercial stocks originate primarily from captive breeding programmes. Wild collection is rare compared to farm-raised individuals.

Questions people ask about X-ray tetra

What makes this fish unique visually?

Its body is translucent, allowing viewers to see the spine and internal organs clearly. Scales appear yellowish-silver with golden tones. Fins show red, black, yellow, and white markings.

Where does this species live naturally?

It inhabits South America. Specific locations include the Amazon and Orinoco rivers in Brazil and Venezuela. Coastal rivers in the Guianas also contain populations. They prefer slow or still waters with plants.

Is it difficult to keep in an aquarium?

No, it is considered hardy and easy to maintain. This resilience makes it suitable for beginners entering the hobby. Most trade specimens come from captive breeding rather than wild capture.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Pristella maxillaris", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

Like X-ray tetra

All other fish
🇨🇩 Democratic Republic of the CongoCongo tetra A colourful African freshwater fish kept in home aquaria for its bright scales and feathery tail.Other · Rivers and lakes · 1899 🇧🇷 Brazil and 4 moreMarbled hatchetfish A small South American freshwater fish kept in aquariums for its unique shape and surface-dwelling habits.Other · Rivers and lakes · 1864 🇧🇼 Botswana and 1 moreAfrican tigerfish Predatory freshwater fish known for sharp teeth and leaping hunting behaviour.Other · Rivers and lakes · 1861 🇧🇷 Brazil and 2 moreCardinal tetra Small freshwater fish with a bright red belly and iridescent blue stripe.Other · Rivers and lakes · 1956

More from Acestrorhamphidae

All of them
Serpae tetra 🇧🇷 Brazil and 4 moreSerpae tetra Small red freshwater fish from South AmericaOther · Rivers and lakes · 1882 🇵🇾 Paraguay and 3 moreBuenos Aires tetra Hardy silver freshwater fish with red fins and a black tail mark.Other · Rivers and lakes · 1907 🇻🇪 VenezuelaDiamond tetra Small Venezuelan freshwater fish with violet finsOther · Rivers and lakes · 1920 🇧🇷 BrazilRummy-nose tetra Small Amazonian characin with a red head and striped tail.Other · Rivers and lakes · 1924

Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

The weekly digest

Every Monday: the fish of the day, new pages on EveryFish, and the conferences and anniversaries of the week ahead.