X-ray tetra care guide
Also called: Pristella tetra, X-ray fish, Water goldfinch, Golden pristella tetra
The X-ray tetra is a hardy, see-through shoaling fish about 1.8 in (4.5 cm) long, with bold yellow, black and white fin markings. It suits beginners and adapts to many water types. Keep six or more in a 15 gallon (57 L) tank or larger.
X-ray tetras need a tank of at least 15 gallons (57 L), a group of 6 or more, and water at 24–28°C (75–82°F) with a pH of 6–7.5. They grow to about 4.5 cm (1.8 in) and are peaceful.
Plan a tank with x-ray tetrasSee all tank mates
X-ray tetra quick facts
| Scientific name | Pristella maxillaris |
|---|---|
| Family | Acestrorhamphidae |
| Origin | Coastal rivers of Venezuela, the Guianas and northern Brazil, plus the Amazon and Orinoco basins (most are farm-bred) |
| Adult size | 4.5 cm (1.8 in) |
| Minimum tank | 15 gallons (57 L), at least 60 cm (24 in) long |
| Temperature | 24–28°C (75–82°F) |
| pH | 6–7.5 |
| Hardness (GH) | 2–20 dGH |
| Group size | 6 or more (shoaling fish) |
| Temperament | Peaceful |
| Swims at | Middle |
| Diet | Omnivore |
| Care level | Easy |
| Lifespan | 3–5 years |
| Safe with shrimp? | Mostly (eats baby shrimp) |
| Safe with plants? | Yes |
Tank setup
A 15 gallon (57 L) tank about 24 in (60 cm) long is enough for a starter group of six. Plants, driftwood and a darker substrate help them feel safe and bring out the fin colors. Leave an open area in the middle for swimming. In a bare, bright tank they tend to look washed out.
How many x-ray tetras in a tank?
The smallest common tank that suits x-ray tetras is a 15 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.
| Tank | X-ray tetras (alone) |
|---|---|
| 3 gallon | Too small |
| 5 gallon | Too small |
| 10 gallon | Too small |
| 15 gallon | 6–17 |
| 20 gallon | 6–22 |
| 20 gallon long | 6–22 |
| 29 gallon | 6–33 |
| 40 gallon | 6–45 |
| 55 gallon | 6–62 |
| 75 gallon | 6–85 |
| 125 gallon | 6–142 |
What you need for x-ray tetras
Sized for a 15 gallon tank, the smallest common size that suits a group of 6 x-ray tetras. For a different tank or a mix of fish, use the stocking calculator for a list sized to your plan.
Tank and equipment
- 15 gallon aquarium (tank or kit) (opens Amazon in a new tab)Bigger tanks are more stable and easier for beginners. How to choose
- Adjustable heater, 75 W (opens Amazon in a new tab)Holds about 79 °F (26 °C) in a room at 65 °F (18 °C). How to choose
- Aquarium thermometer (opens Amazon in a new tab)Check it daily: heaters can fail stuck on or off. How to choose
- Hang-on-back filter rated 60–90 GPH (opens Amazon in a new tab)Community tank: 4–6 times the tank volume per hour. How to choose
- About 35 lb of aquarium gravel (opens Amazon in a new tab)Enough for a layer about 2 in (5 cm) deep. Smooth gravel suits most community fish. How to choose
- Water conditioner (dechlorinator) (opens Amazon in a new tab)Removes chlorine and chloramine from tap water. Seachem Prime is a popular, concentrated choice. How to choose
- Liquid test kit (ammonia, nitrite, nitrate, pH) (opens Amazon in a new tab)Liquid kits are more accurate than strips. The API Freshwater Master Test Kit is the common choice. How to choose
- Gravel vacuum (siphon) (opens Amazon in a new tab)Cleans the gravel and does the water change in one go. How to choose
- LED aquarium light, about 24 in long (opens Amazon in a new tab)Match the light to the tank length. Basic LEDs grow easy plants. How to choose
Food and extras for x-ray tetras
- Micro pellets or flakes for small fish (opens Amazon in a new tab)Small enough for tetras, rasboras and other nano fish.
Product links go to Amazon search results. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Disclosure.
Water parameters
Keep it at 24–28 °C (75–82 °F) with pH 6.0–7.5. It handles soft to fairly hard water, roughly 2–20 dGH, so it fits into most community tanks. Wild fish can live in slightly salty coastal water, but yours should be kept in normal fresh water.
Best tank mates for x-ray tetras
These popular species share x-ray tetras' water needs and temperament. See the full list of 84 good matches.
Betta fish
6.5 cm (2.6 in) · 24–28°C (75–82°F)
Cherry shrimp
3 cm (1.2 in) · 20–27°C (68–81°F)
Nerite snail
2.5 cm (1 in) · 22–27°C (72–81°F)
Guppy
5 cm (2 in) · 22–27°C (72–81°F)
Dwarf gourami
7.5 cm (3 in) · 24–28°C (75–82°F)
Bristlenose pleco
12 cm (4.7 in) · 22–26°C (72–79°F)
Bronze corydoras
7 cm (2.8 in) · 21–26°C (70–79°F)
Assassin snail
2.5 cm (1 in) · 22–27°C (72–81°F)
Avoid keeping x-ray tetras with
- Common goldfish: They need different temperatures: X-ray tetra 24–28°C (75–82°F), common goldfish 15–22°C (59–72°F).
- Fancy goldfish: They need different temperatures: X-ray tetra 24–28°C (75–82°F), fancy goldfish 18–23°C (64–73°F).
- Oscar: Oscar can eat x-ray tetras: they're small enough to fit in its mouth once it's grown.
- Bala shark: Bala shark can eat x-ray tetras: they're small enough to fit in its mouth once it's grown.
- Chinese algae eater: Chinese algae eater is aggressive and will bully or injure peaceful x-ray tetras.
- Convict cichlid: Convict cichlid is aggressive and will bully or injure peaceful x-ray tetras.
Feeding
In nature it hunts insects and tiny crustaceans, but in the aquarium it eats almost anything. Feed a good flake or micro pellet every day. Offer frozen or live daphnia, brine shrimp and bloodworm a few times a week for best condition.
Behavior
A very peaceful shoaler that stays mostly in the middle of the tank. Big or boisterous fish can bully it or beat it to the food. Good tank mates are other small tetras, rasboras, pencilfish, hatchetfish, corydoras, small plecos and dwarf cichlids. Adult dwarf shrimp are usually safe, but shrimplets may be eaten.
Breeding
Females are bigger and rounder; males are slimmer. Spawning is easy in a dim, separate tank with soft, acidic water and java moss or a spawning mop. The adults eat the eggs, so take them out after spawning. The tiny fry are tricky to raise and need infusoria or very fine food at first.
Tips from experienced keepers
- One of the best small tetras for harder tap water, since it copes with a wide hardness range.
- Keep ten or more if you can. A larger group swims more openly and looks better.
- Golden and albino forms need exactly the same care as the normal fish.
- Feed small amounts two or three times a day rather than one big meal.
Frequently asked questions
Can X-ray tetras live with shrimp?
Usually, yes. They leave adult cherry and amano shrimp alone, but they will eat baby shrimp. Dense plants or moss help shrimplets survive.
How many X-ray tetras should be kept together?
Keep at least six, and ten or more is better. In small groups they get stressed and hide.
What size tank do X-ray tetras need?
A 15 gallon (57 L) tank about 24 in (60 cm) long suits a group of six. A bigger group or a mixed community needs more room.
Sources
We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.