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Encyclopedia / Tetras / X-ray tetra
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Variations

2 kinds · tap one for a closer look

X-ray tetra

Pristella maxillaris · Xray, Pristella, Golden pristella

Peaceful, hardy shoaler.

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4.5 cmAdult size ✓
24–28 °CTemperature ✓
6–7.5pH ✓
54 LSmallest tank ✓
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Tank mates
Check your own mix →
Not recommended
  • Tinfoil barb eats animals up to about 5 cm. X-ray tetra only grows to 4.5 cm.
Not recommended
  • White cloud mountain minnow needs cool water and makes a lot of waste, while X-ray tetra is tropical.
  • They need different temperatures (24–28 °C vs 14–22 °C). No setting suits both.
Not recommended
  • Giant gourami eats animals up to about 10 cm. X-ray tetra only grows to 4.5 cm.
With conditions
  • Only a narrow temperature range suits both: 24–25 °C.
With conditions
  • Only a narrow temperature range suits both: exactly 24 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

373 species in our list are a good match.

Facts checked against sources on 16 Oct 2026. ✓ means a source backs it; ? means no reliable source yet. See sources

Care and water

Hardness ✓2–20 dGH
Group size ✓6 or more
Temperament ✓Peaceful
Swims at ?Middle
Care level ✓Easy
Diet Omnivore
Lifespan ?Unknown
Size in shops 2–3 cm
Growth Medium

Behavior

Peaceful, hardy shoaler.

Food

Flakes, micro-pellets, frozen foods.

Tap a food to see what it is.

Male or female

Male X-ray tetra
Male
Female X-ray tetra
Female

Mature females are usually bigger and noticeably stockier than males.

Health

Common problems. Tap one to see the signs. This is a guide, not a diagnosis.

Breeding

Egg-scatterer · Easy

Spawns among submerged plants; fairly easy to spawn, but the tiny fry are tricky to raise.

Pairing

Buy a group of 6-8; pairs form on their own.

Setup

20 L tank with fine plants or mops. Soft, slightly acidic water.

What starts it

Warm water change and live food feeding.

Eggs

300-400 eggs per spawning; eggs hatch in 24-36 hours and the fry swim freely 3-4 days later.

Raising the fry

Feed infusoria or green water for days 1-3, then newly hatched brine shrimp and microworms. Keep light low early on. Grow out in a larger tank once fish are about 1 cm.

Common mistakes
  • Leaving parents with eggs
  • Hard water
  • Too little cover
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionNorthern South America – Amazon, Orinoco & coastal Guianas
Rivers and lakesLower Amazon, Orinoco and coastal rivers of Guyana, Suriname and French Guiana
HabitatCoastal streams and swamps, sometimes slightly brackish
Native rangeAbout 1,500 km across
See it on the world map

The story of the x-ray tetra

Its see-through body gives it the name X-ray tetra. It lives in calm coastal fresh waters and densely planted swamps of northern South America. The genus name Pristella means "little saw", probably for its tiny jaw teeth.

Albert B. Ulrey described this little tetra in 1894. Its nearly transparent body, which shows the swim bladder, earned it the name 'X-ray tetra'. It has been kept and bred by aquarists for many decades.

First described by Albert B. Ulrey in 1894.

  • You can see its silvery swim bladder through its see-through body.
  • Some wild populations live in coastal waters with a little salt.
  • Its yellow, black and white dorsal fin pattern is a quick identification mark.

Sources

15 facts checked with sources