Not furry, but we like them anyway.
X-ray Tetra
Pristella maxillaris
Also called Pristella tetra, Water goldfinch, X-ray fish
From Northern South America: the Amazon and Orinoco basins and the coastal rivers of Venezuela, the Guianas and northern Brazil123
A friendly guide, not veterinary advice. For anything about your pet's health, ask your vet.
At a glance the quick version
Looks how to spot one
Small scaled characin (tetra) with an adipose fin
A see-through little tetra whose backbone can be made out through its flanks. The scales have a silvery-yellow, slightly golden shine and the tail is tinged red. The dorsal and anal fins each carry a striking patch of black framed by yellow and white, and a small round dark spot sits just behind the gills. Grown females are larger and stockier than males.32
Personality what they are like
A gentle, gregarious tetra that keeps to its group and does not bother other fish. It is happiest with calm companions of a similar size and can be pushed aside at feeding time by much bigger or rowdier tankmates.21
Daily activity how busy a day looks
An active mid-water swimmer that moves around as a loose shoal; it appreciates open swimming space between plants.2
Grooming and care the hands-on bits
Low-maintenance: steady, clean water with regular partial water changes suits it. Captive-bred fish adapt to a wide range of water conditions.21
Home where they are happiest
Tank with a base of at least 60 x 30 cm (about 54 litres). Water 22-28 °C, pH 6.0-7.5 (FishBase gives 6.0-8.0), hardness 2-20 dGH. Plants and some cover help it feel secure.21
Food basics what goes in the bowl
A small micropredator that eats worms, tiny crustaceans and insects in the wild. In the aquarium offer quality flakes or granules plus small live or frozen foods such as Daphnia and brine shrimp.21
Company who they like around
A shoaling fish: keep at least 6, and ideally 10 or more. Mixes well with other peaceful South American fish and general community species.21
The story where it all began
The X-ray tetra was described scientifically by American biologist Albert B. Ulrey in 1894, originally under the name Aphyocharax maxillaris. Carl Eigenmann later created the genus Pristella for it, and it is still the only species in that genus. It has long been one of the classic beginner tetras, and nearly all fish in shops today are captive-bred.321
Fun facts for the dinner table
- 1
Its body is so translucent that you can see its spine from the outside, which is how it earned the name X-ray tetra.3
- 2
The genus name Pristella comes from a Greek word for a saw, a nod to the fish's tiny pointed teeth.3
- 3
It is the only member of its genus.2
- 4
In the rainy season wild fish move into flooded savannah and spawn among drowned plants.2
- 5
A spawning can produce about 300 to 400 eggs.1
Recognised by the official bits
- IUCN Red List
- Least Concern (assessed 16 November 2020)1
- FishBase
- Listed as a popular species in the aquarium trade1
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a X-ray Tetra. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
Owner questions the things everyone asks
How often should I feed my X-ray Tetra?
Feed small amounts once or twice a day. Furry Diary's starting plan is to feed daily, giving only what they can eat in a couple of minutes.21 Furry Diary plan
What does a X-ray Tetra eat, and what should it never eat?
Offer quality flakes or granules plus small live or frozen foods like Daphnia and brine shrimp. Avoid any large or hard foods that could harm their tiny mouths.21
How much space does a X-ray Tetra need?
A tank with a base of at least 60 x 30 cm (about 54 litres) is recommended. This gives them room to swim as a shoal.21
What temperature, light or water does a X-ray Tetra need?
Keep water temperature between 22-28°C, pH 6.0-7.5 (up to 8.0 is possible), and hardness 2-20 dGH. Normal aquarium lighting is fine, and plants or cover help them feel secure.21
How often should I clean a X-ray Tetra's home?
Furry Diary's starting plan suggests a weekly 25% water change, weekly glass cleaning, and a monthly filter rinse in old tank water (never tap water). Regular testing keeps water stable. Furry Diary plan
Can a X-ray Tetra live with others?
Yes, they are gentle shoaling fish that should be kept in groups of at least 6, ideally 10 or more. They mix well with other peaceful South American and community fish of similar size.21
How long does a X-ray Tetra live?
Lifespan varies depending on care and conditions. For specific expectations, ask a good breeder or an exotic-pet vet.
Can I handle a X-ray Tetra?
No, these are delicate fish that should never be handled. Always use a net and keep them in water to avoid stress or injury.21
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Furry Diary's own starting care plan. A friendly guide, not a vet's advice.
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at support@furrydiary.app and we will fix it.
- FishBase species summary: Pristella maxillaris fishbase.seused for describer, maximum length, distribution, water range, IUCN status
- Seriously Fish species profile: Pristella maxillaris seriouslyfish.comused for aquarium care, water parameters, behaviour, diet, sexing, habitat
- Wikipedia: X-ray tetra en.wikipedia.orgused for taxonomy history, etymology, appearance
- VCA Animal Hospitals: Feeding times and frequency for your dog vcahospitals.comused for owner questions
- ASPCA: Dog grooming tips aspca.orgused for owner questions
- ASPCA: Cat grooming tips aspca.orgused for owner questions
- ASPCA: People foods to avoid feeding your pets aspca.orgused for owner questions
- RSPCA: What to feed your rabbit rspca.org.ukused for owner questions
Checked 2026-09-30. Text is written in our own words from these sources.