Photo: Debivort (CC BY-SA 3.0) — via Wikimedia Commons
X-ray Tetra (Pristella maxillaris)
A translucent, black-and-yellow-striped schooler tough enough for beginners yet elegant enough for any planted community tank.
Will it live with a X-ray Tetra?
We compare each fish against your x-ray tetra on temperament, size, water parameters and swimming zone. Set your tank size and filter the results.
- Amano Shrimp✅ CompatiblePeaceful · 5 cm · Easy care · 18–28 °C (64–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Axelrod's Cory✅ CompatiblePeaceful · 5 cm · Easy care · 23–28 °C (73–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Axelrod's Cory in a shoal of 6+ or it gets stressed and nippy.
- Bandit Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 22–27 °C (72–81 °F)
- Both are peaceful, and their water overlaps around 22–27 °C — no size, zone or temperament conflicts.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Bandit Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Black Phantom Tetra✅ CompatiblePeaceful · 4.5 cm · Easy care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Phantom Tetra in a shoal of 6+ or it gets stressed and nippy.
- Blue Turbo Snail✅ CompatiblePeaceful · 5 cm · Medium care · 25–30 °C (77–86 °F)
- Compatible on the things that matter: shared water near 25–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Checkered Barb✅ CompatiblePeaceful · 5 cm · Easy care · 20–25 °C (68–77 °F)
- Both are peaceful, and their water overlaps around 22–25 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Checkered Barb in a shoal of 6+ or it gets stressed and nippy.
- Cherry Barb✅ CompatiblePeaceful · 5 cm · Easy care · 23–27 °C (73–81 °F)
- Both are peaceful, and their water overlaps around 23–27 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Cherry Barb in a shoal of 6+ or it gets stressed and nippy.
- Chocolate Gourami✅ CompatiblePeaceful · 5 cm · Hard care · 25–30 °C (77–86 °F)
- Compatible on the things that matter: shared water near 25–28 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Chocolate Gourami in a shoal of 6+ or it gets stressed and nippy.
- Cochu's Blue Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Cochu's Blue Tetra in a shoal of 8+ or it gets stressed and nippy.
- Firehead Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 24–28 °C (75–82 °F)
- Both are peaceful, and their water overlaps around 24–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Firehead Tetra in a shoal of 8+ or it gets stressed and nippy.
- Five-banded Barb✅ CompatiblePeaceful · 5 cm · Easy care · 23–27 °C (73–81 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Five-banded Barb in a shoal of 6+ or it gets stressed and nippy.
- Forktail Blue-eye✅ CompatiblePeaceful · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Forktail Blue-eye in a shoal of 6+ or it gets stressed and nippy.
- Gold Tetra✅ CompatiblePeaceful · 4.5 cm · Easy care · 23–28 °C (73–82 °F)
- Both are peaceful, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Gold Tetra in a shoal of 6+ or it gets stressed and nippy.
- Half-striped Penguin Tetra✅ CompatiblePeaceful · 5 cm · Medium care · 23–28 °C (73–82 °F)
- Both are peaceful, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Half-striped Penguin Tetra in a shoal of 6+ or it gets stressed and nippy.
- Harlequin Rasbora✅ CompatiblePeaceful · 5 cm · Easy care · 23–28 °C (73–82 °F)
- Both are peaceful, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Harlequin Rasbora in a shoal of 6+ or it gets stressed and nippy.
- Honey Gourami✅ CompatiblePeaceful · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Horseman Cory✅ CompatiblePeaceful · 5 cm · Medium care · 22–26 °C (72–79 °F)
- Compatible on the things that matter: shared water near 22–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Horseman Cory in a shoal of 6+ or it gets stressed and nippy.
- Japanese Trapdoor Snail✅ CompatiblePeaceful · 5 cm · Easy care · 10–28 °C (50–82 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Julii Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 23–26 °C (73–79 °F)
- Both are peaceful; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Julii Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Lemon Tetra✅ CompatiblePeaceful · 4.5 cm · Easy care · 23–28 °C (73–82 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Lemon Tetra in a shoal of 6+ or it gets stressed and nippy.
- Masked Corydoras✅ CompatiblePeaceful · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Both are peaceful, and their water overlaps around 22–28 °C — no size, zone or temperament conflicts.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Masked Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Mystery Snail✅ CompatiblePeaceful · 5 cm · Easy care · 20–28 °C (68–82 °F)
- Compatible on the things that matter: shared water near 22–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Panda Corydoras✅ CompatiblePeaceful · 5 cm · Medium care · 20–26 °C (68–79 °F)
- Compatible on the things that matter: shared water near 22–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Panda Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Yellow Tetra✅ CompatiblePeaceful · 4.5 cm · Easy care · 20–25 °C (68–77 °F)
- Both are peaceful, and their water overlaps around 22–25 °C — no size, zone or temperament conflicts.
- Both favour the middle of the tank — offer enough cover so they aren't always in each other's space.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Yellow Tetra in a shoal of 6+ or it gets stressed and nippy.
- Black Ruby Barb⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 22–26 °C (72–79 °F)
- Black Ruby Barb is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~100 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Ruby Barb in a shoal of 6+ or it gets stressed and nippy.
- Black Skirt Tetra⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 20–26 °C (68–79 °F)
- Black Skirt Tetra is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Black Skirt Tetra in a shoal of 6+ or it gets stressed and nippy.
- Desert Goby⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 18–28 °C (64–82 °F)
- Desert Goby is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Dwarf Chain Loach⚠️ With cautionPeaceful · 6 cm · Medium care · 24–29 °C (75–84 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Dwarf Chain Loach in a shoal of 6+ or it gets stressed and nippy.
- Eastern Betta⚠️ With cautionSemi-aggressive · 6 cm · Medium care · 24–28 °C (75–82 °F)
- Eastern Betta is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Ghost Shrimp⚠️ With cautionPeaceful · 4 cm · Easy care · 18–28 °C (64–82 °F)
- X-ray Tetra may eat Ghost Shrimp or pick off its shrimplets — a densely planted tank with moss gives them a fighting chance.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Ghost Shrimp in a shoal of 6+ or it gets stressed and nippy.
- GloFish Tetra⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 21–28 °C (70–82 °F)
- GloFish Tetra is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep GloFish Tetra in a shoal of 6+ or it gets stressed and nippy.
- Humpbacked Tetra⚠️ With cautionSemi-aggressive · 5 cm · Hard care · 24–28 °C (75–82 °F)
- Expect Humpbacked Tetra to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Humpbacked Tetra in a shoal of 8+ or it gets stressed and nippy.
- Morse Code Corydoras⚠️ With cautionPeaceful · 5 cm · Medium care · 23–26 °C (73–79 °F)
- Your 75 L tank is below the ~80 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Morse Code Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Odessa Barb⚠️ With cautionSemi-aggressive · 6 cm · Easy care · 20–26 °C (68–79 °F)
- Odessa Barb is semi-aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Odessa Barb in a shoal of 6+ or it gets stressed and nippy.
- Peaceful Betta⚠️ With cautionSemi-aggressive · 6 cm · Medium care · 24–28 °C (75–82 °F)
- Expect Peaceful Betta to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Silvertip Tetra⚠️ With cautionSemi-aggressive · 5 cm · Easy care · 22–28 °C (72–82 °F)
- Expect Silvertip Tetra to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Keep Silvertip Tetra in a shoal of 6+ or it gets stressed and nippy.
- Smaragd Betta⚠️ With cautionAggressive · 6 cm · Medium care · 23–28 °C (73–82 °F)
- Expect Smaragd Betta to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Spotfin Betta⚠️ With cautionSemi-aggressive · 5 cm · Medium care · 23–28 °C (73–82 °F)
- Spotfin Betta and X-ray Tetra are close in size, but the semi-aggressive one tends to dominate — add x-ray tetra in a group to spread the pressure.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Striped Red-Eye Puffer⚠️ With cautionAggressive · 5 cm · Hard care · 24–28 °C (75–82 °F)
- Striped Red-Eye Puffer is aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Wine Red Betta⚠️ With cautionAggressive · 5 cm · Medium care · 24–28 °C (75–82 °F)
- Expect Wine Red Betta to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Alligator Gar⛔ Not recommendedAggressive · 250 cm · Hard care · 24–28 °C (75–82 °F)
- Size gap is too large (250 vs 4.5 cm): Alligator Gar will treat X-ray Tetra as food.
- Alligator Gar clearly outsizes X-ray Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~3785 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Clown Knifefish⛔ Not recommendedAggressive · 90 cm · Hard care · 24–28 °C (75–82 °F)
- X-ray Tetra is bite-sized to a 90 cm predatory clown knifefish — it will be eaten.
- Clown Knifefish clearly outsizes X-ray Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~750 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Fire Eel⛔ Not recommendedSemi-aggressive · 100 cm · Medium care · 24–28 °C (75–82 °F)
- X-ray Tetra is bite-sized to a 100 cm predatory fire eel — it will be eaten.
- Expect Fire Eel to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~380 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Koi⛔ Not recommendedPeaceful · 90 cm · Medium care · 4–28 °C (39–82 °F)
- Size gap is too large (90 vs 4.5 cm): Koi will treat X-ray Tetra as food.
- Your 75 L tank is below the ~3800 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Redtail Catfish⛔ Not recommendedAggressive · 120 cm · Hard care · 24–27 °C (75–81 °F)
- Redtail Catfish (120 cm) is big enough to swallow the 4.5 cm X-ray Tetra whole.
- Expect Redtail Catfish to harass X-ray Tetra at times; give dense cover and watch them at feeding.
- Your 75 L tank is below the ~5700 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Spotted Gar⛔ Not recommendedAggressive · 90 cm · Hard care · 18–26 °C (64–79 °F)
- X-ray Tetra is bite-sized to a 90 cm predatory spotted gar — it will be eaten.
- Spotted Gar clearly outsizes X-ray Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~600 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Wels Catfish⛔ Not recommendedAggressive · 300 cm · Hard care · 15–25 °C (59–77 °F)
- Size gap is too large (300 vs 4.5 cm): Wels Catfish will treat X-ray Tetra as food.
- Wels Catfish is aggressive and may chase or nip the smaller X-ray Tetra — plant heavily and break up sight lines.
- Your 75 L tank is below the ~20000 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
- Wolf Cichlid⛔ Not recommendedAggressive · 72 cm · Hard care · 24–30 °C (75–86 °F)
- Wolf Cichlid (72 cm) is big enough to swallow the 4.5 cm X-ray Tetra whole.
- Wolf Cichlid clearly outsizes X-ray Tetra and is aggressive; risky unless the tank is big and well-planted.
- Your 75 L tank is below the ~760 L this pairing really wants — crowding raises aggression.
- Keep X-ray Tetra in a shoal of 6+ or it gets stressed and nippy.
Compatibility is computed from each species' care data — a strong starting point, not a guarantee. Individual temperament varies, so always introduce new fish slowly and watch them.
X-ray Tetra care specs
- Care level
- Easy
- Breeding
- Medium
- Max size
- 4.5 cm (1.8 in)
- Min tank size
- 75 L (19.8 gal)
- Temperature
- 22–28 °C (72–82 °F)
- pH
- 6–7.5
- Hardness
- 2–15 dGH
- Lifespan
- 3–5 years
- Diet
- Omnivore
- Swim level
- Middle
- Group size
- 6+ (shoaling)
- Family
- Characidae
- Origin
- South America — coastal rivers of Venezuela, Guyana, Suriname and northern Brazil (Orinoco basin)
What is an X-ray Tetra?
The X-ray tetra (Pristella maxillaris) is a small, peaceful South American characin that earns its name from one of the most distinctive features in the freshwater hobby: a nearly transparent body through which you can see the spine and internal organs. Mature fish reach about 4.5 cm (1.75 in), making them one of the more compact schooling tetras available. What they lack in size they make up for in collective visual impact — a shoal of a dozen or more X-ray tetras moving through a planted tank looks like a shimmering, luminous curtain.
Their translucent silver flanks are set off by bold patterning on the dorsal and anal fins: bands of yellow, black and white that flash as the school turns. Unlike many “fancy” aquarium fish, this is the natural wild-type coloration — there are no selectively bred long-fin or neon morphs to worry about. The species is robust enough for beginners yet refined enough to anchor a show-quality aquascape, a genuinely useful combination.
Where do X-ray Tetras come from?
X-ray tetras are native to coastal river systems in northeastern South America, from northern Brazil through Guyana, Suriname and Venezuela, including tributaries of the Orinoco basin. Their natural habitat is varied: slow-moving, often tea-dark blackwater rivers, seasonally flooded savannahs and coastal lowland streams. This breadth of habitat is exactly why Pristella maxillaris tolerates a wider range of water parameters than many of its Amazonian relatives.
In the wild they form large, fast-moving schools in open water, staying near vegetation or submerged roots where they shelter from predators. Understanding this tells you most of what you need to know about keeping them happy in an aquarium: they want company, moderate flow, plenty of mid-water swimming space, and the option to retreat to planted cover.
What Size Tank Does an X-ray Tetra Need?
The practical minimum is 75 litres (20 gallons) for a school of six, and more water is always better. X-ray tetras are active, mid-water schoolers that use horizontal space — a longer, shallower tank suits them better than a tall column-style aquarium. A 90 cm (36 in) footprint gives the shoal room to form proper formation and behave naturally.
Provide a mix of open swimming lanes and planted margins. Dense plantings of stem plants and fine-leaved species like java fern or hornwort serve as shelter and make the translucent fish pop visually. A dark substrate amplifies the iridescent sheen of the school. Leave a clear area across the middle of the tank for the shoal to cruise; they will use it constantly. A tight-fitting lid is sensible — tetras are capable jumpers when startled.
What Water Parameters Do X-ray Tetras Need?
One of the X-ray tetra’s greatest strengths is its adaptability:
- Temperature: 22–28 °C (72–82 °F)
- pH: 6.0–7.5
- Hardness: 2–15 dGH (soft to moderately hard)
This broad window means the X-ray tetra is compatible with most community tanks running neutral, slightly soft tap water — no reverse-osmosis unit required. It also makes them easier bedfellows with the full range of common community fish. As always, stability matters more than chasing specific numbers: a cycled tank with consistent weekly water changes of 25–30% will keep parameters steady and fish thriving. Sudden swings in temperature or pH are the real enemy.
Moderate, gentle filtration that turns the tank volume over roughly four to five times per hour suits them well. Strong powerheads or aggressive surface agitation are unnecessary and can push a tight school around uncomfortably.
What Do X-ray Tetras Eat?
X-ray tetras are omnivores with a modest appetite that matches their small size. In the wild they pick off zooplankton, small invertebrates and plant matter. In the aquarium, a rotating diet of the following covers all nutritional bases:
- Staple: High-quality micro-pellets or fine-grade flake sized for small tetras.
- Protein boost: Small frozen or live foods — daphnia, baby brine shrimp, micro-worms or finely chopped bloodworm. These trigger natural feeding frenzy behaviour and keep colour and condition excellent.
- Variety: Blanched spirulina flake or vegetable-based pellets once or twice a week rounds out the omnivore diet.
Feed once or twice daily, offering only as much as the school consumes in two to three minutes. Uneaten food sinks, fouls the substrate and stresses water quality. Because these fish are small-mouthed, make sure any food particle is appropriately sized — standard flake is usually fine once crushed slightly.
Are X-ray Tetras Aggressive — and What Fish Can Live with Them?
X-ray tetras are genuinely peaceful. They do not nip fins, they do not harass smaller fish, and they do not hold territory within the school. Their only social requirement is that they must be kept in a group: a lone X-ray tetra or a pair will be stressed, hide constantly and may fade in colour. Keep a minimum of six, and aim for ten or more if the tank size allows — larger shoals produce the impressive, coordinated movement that makes this fish special.
They are excellent community fish with a wide range of similarly sized peaceful species. Classic companions include neon tetras, harlequin rasboras, corydoras catfish, dwarf gouramis, and small loaches that share the same water parameter range. Avoid large, predatory species (anything that would fit a 4.5 cm fish in its mouth) and known fin-nippers like tiger barbs.
For a full list of tested compatible and incompatible pairings, see X-ray Tetra tank mates.
How Do You Tell Male and Female X-ray Tetras Apart?
Sexual dimorphism in Pristella maxillaris is subtle and most obvious when females are in breeding condition. Females become noticeably rounder and deeper-bodied as the abdomen fills with eggs — in a ripe female this is visible from across the tank. Males remain slimmer and trimmer in the belly at all times.
Outside of breeding condition, distinguishing individual fish by sex is genuinely difficult. Fin length, coloration and overall size are not reliable indicators in this species. If you plan to breed them, buy a group of eight to ten and let nature sort out the sex ratio — you will almost certainly end up with both.
How Do X-ray Tetras Breed?
Breeding X-ray tetras is achievable with some preparation, earning it a medium difficulty rating. They are egg scatterers: the male courts the female with a brief display, and spawning occurs in open water or among fine-leaved plants, with eggs dropping to the substrate. The parents show no brood care and will readily eat both eggs and fry if left in the same tank.
To breed them intentionally:
- Set up a dedicated breeding tank of around 30–40 L with very soft, slightly acidic water (pH 6.0–6.5, near-zero hardness), dim lighting and a fine-leaved plant or spawning mop covering the bottom.
- Condition a pair or small group on live and frozen foods for one to two weeks before introducing them to the breeding tank.
- Spawning typically occurs in the early morning. After eggs are laid, remove the adults immediately.
- Eggs hatch in roughly 24–36 hours at 26–28 °C (79–82 °F). Feed hatched fry infusoria or commercial fry powder initially, graduating to baby brine shrimp as they grow.
Water quality in the fry tank is critical — tiny, frequent water changes prevent ammonia spikes without shocking the delicate larvae.
What Are Common X-ray Tetra Diseases?
X-ray tetras are hardy for their size, but they are not immune to the standard community-tank ailments:
- Ich (white spot): Fine white grains across fins and body, accompanied by scratching against decor. The most common stress-related disease; most often triggered by temperature drops or introducing infected fish without quarantine.
- Fin rot: Ragged or receding fin edges, usually caused by bacterial infection following poor water quality or injury. Improving water conditions is the first response.
- Velvet (Oodinium): A dusty gold or rust-coloured sheen on the skin. Can spread quickly through a school; dim the lights, which helps slow the parasite, and act promptly.
- Internal parasites: Hollow belly in an otherwise active, feeding fish can indicate internal worms, more common in wild-caught stock.
Prevention is straightforward: maintain a cycled, stable tank; quarantine all new fish for two to four weeks before adding them to the community; avoid sudden temperature swings; and feed a varied diet to keep immune function strong.
Health note: disease diagnosis and medication selection are beyond the scope of a care profile. Always confirm symptoms against a reputable veterinary or fish-health source before medicating, and follow product instructions precisely.
How Long Do X-ray Tetras Live?
With good care, X-ray tetras live 3–5 years. They are not a short-lived novelty fish — a well-maintained school will be with you for several years and reward consistent husbandry with vibrant schooling behaviour and strong condition. The keys are familiar: stable, clean water; a species-appropriate diet; a large enough group; and a tank sized to let them express natural behaviour. Provide those, and these translucent little fish will remain one of the most reliably rewarding community species in the hobby.
Frequently asked questions
Why is the X-ray tetra see-through?
The translucency comes from very thin, unpigmented muscle tissue and a nearly clear body cavity. You can often see the spine and internal organs. It's a natural adaptation, not a product of selective breeding, and every individual in the species shares it — making the school look like a shimmering silver wave under aquarium lighting.
Can X-ray tetras live with soft-water tetras like neons?
Yes — they overlap nicely on water parameters and temperament. X-ray tetras are actually more tolerant of a wider pH and hardness range than neons, so they're often described as the hardier, easier-to-keep alternative. Keep both species in groups of six or more and give them a planted tank with some open swimming space in the middle.
What you need to keep a x-ray tetra
The baseline is a heated, filtered 75 L+ tank: a reliable heater to hold 22–28 °C (72–82 °F), a gentle filter that won't batter a x-ray tetra in the current, and a tight-fitting lid. Cycle the tank fully before adding any fish.
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