Photo: Ltshears - Trisha M Shears (Public domain) — via Wikimedia Commons
Bucktooth Tetra (Exodon paradoxus)
A glittering, fast-moving scale-eater that belongs in a large, single-species school — one of the hobby's most spectacular predatory tetras.
Will it live with a Bucktooth Tetra?
We compare each fish against your bucktooth tetra on temperament, size, water parameters and swimming zone. Set your tank size and filter the results.
- Banjo Catfish✅ CompatiblePeaceful · 15 cm · Medium care · 20–26 °C (68–79 °F)
- Compatible on the things that matter: shared water near 23–26 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Bearded Corydoras✅ CompatiblePeaceful · 10 cm · Medium care · 18–24 °C (64–75 °F)
- Compatible on the things that matter: shared water near 23–24 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Bearded Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Black Kuhli Loach✅ CompatiblePeaceful · 8 cm · Easy care · 23–28 °C (73–82 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Bolivian Ram✅ CompatiblePeaceful · 8 cm · Medium care · 24–28 °C (75–82 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Bristlenose Pleco✅ CompatiblePeaceful · 12 cm · Easy care · 23–30 °C (73–86 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Burmese Loach✅ CompatiblePeaceful · 9 cm · Easy care · 22–28 °C (72–82 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Clown Pleco✅ CompatiblePeaceful · 9 cm · Medium care · 24–28 °C (75–82 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Giant Kuhli Loach✅ CompatiblePeaceful · 12 cm · Easy care · 24–30 °C (75–86 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Kuhli Loach✅ CompatiblePeaceful · 10 cm · Easy care · 24–30 °C (75–86 °F)
- Compatible on the things that matter: shared water near 24–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Leopard Frog Pleco✅ CompatiblePeaceful · 9 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 Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Marbled Hoplo✅ CompatiblePeaceful · 14 cm · Easy care · 22–28 °C (72–82 °F)
- Compatible on the things that matter: shared water near 23–28 °C, workable temperaments, and no predator-and-prey size gap.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Medusa Pleco✅ CompatiblePeaceful · 12 cm · Medium care · 26–30 °C (79–86 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Pantanal Corydoras✅ CompatiblePeaceful · 8 cm · Medium care · 22–27 °C (72–81 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Pantanal Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Peppered Corydoras✅ CompatiblePeaceful · 7 cm · Easy care · 18–26 °C (64–79 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Peppered Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Porthole Catfish✅ CompatiblePeaceful · 10 cm · Easy care · 22–28 °C (72–82 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–28 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Rubber Lip Pleco✅ CompatiblePeaceful · 12 cm · Easy care · 20–26 °C (68–79 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Snowball Pleco✅ CompatiblePeaceful · 16 cm · Medium care · 24–30 °C (75–86 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Spotted Corydoras✅ CompatiblePeaceful · 7 cm · Easy care · 22–27 °C (72–81 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Spotted Corydoras in a shoal of 6+ or it gets stressed and nippy.
- Spotted Rubbernose Pleco✅ CompatiblePeaceful · 12 cm · Medium care · 20–26 °C (68–79 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Spotted Talking Catfish✅ CompatiblePeaceful · 15 cm · Easy care · 22–26 °C (72–79 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Striped Eel Loach✅ CompatiblePeaceful · 12 cm · Medium care · 24–28 °C (75–82 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Upside-down Catfish✅ CompatiblePeaceful · 10 cm · Easy care · 22–26 °C (72–79 °F)
- Aggressive + Peaceful, but with no direct clash here; temperature, pH and hardness ranges all overlap and neither outsizes the other enough to be a threat.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Zebra Loach✅ CompatiblePeaceful · 9 cm · Medium care · 23–26 °C (73–79 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 23–26 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Zebra Pleco✅ CompatiblePeaceful · 10 cm · Hard care · 26–30 °C (79–86 °F)
- Aggressive + Peaceful, but with no direct clash here, and their water overlaps around 26–28 °C — no size, zone or temperament conflicts.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Amazon Puffer⚠️ With cautionPeaceful · 8 cm · Medium care · 23–28 °C (73–82 °F)
- Bucktooth Tetra is aggressive and may chase or nip the smaller Amazon Puffer — plant heavily and break up sight lines.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Amazon Puffer in a shoal of 6+ or it gets stressed and nippy.
- Boesemani Rainbowfish⚠️ With cautionPeaceful · 11 cm · Medium care · 24–28 °C (75–82 °F)
- Expect Bucktooth Tetra to harass Boesemani Rainbowfish at times; give dense cover and watch them at feeding.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Boesemani Rainbowfish in a shoal of 6+ or it gets stressed and nippy.
- Brilliant Rasbora⚠️ With cautionPeaceful · 9 cm · Easy care · 22–28 °C (72–82 °F)
- Bucktooth Tetra and Brilliant Rasbora are close in size, but the aggressive one tends to dominate — add brilliant rasbora in a group to spread the pressure.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Brilliant Rasbora in a shoal of 6+ or it gets stressed and nippy.
- Clown Rasbora⚠️ With cautionPeaceful · 10 cm · Medium care · 23–28 °C (73–82 °F)
- Bucktooth Tetra is aggressive and may chase or nip the smaller Clown Rasbora — plant heavily and break up sight lines.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Clown Rasbora in a shoal of 6+ or it gets stressed and nippy.
- Denison Barb⚠️ With cautionPeaceful · 15 cm · Medium care · 18–25 °C (64–77 °F)
- Bucktooth Tetra is a notorious fin-nipper — even though Denison Barb is larger, an active shoal will harass its trailing fins. Only safe in a full group of 8+ with plenty of cover.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Denison Barb in a shoal of 6+ or it gets stressed and nippy.
- Giant Betta⚠️ With cautionPeaceful · 12 cm · Medium care · 24–28 °C (75–82 °F)
- Expect Bucktooth Tetra to harass Giant Betta at times; give dense cover and watch them at feeding.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Giant Danio⚠️ With cautionPeaceful · 10 cm · Easy care · 20–27 °C (68–81 °F)
- Bucktooth Tetra and Giant Danio are close in size, but the aggressive one tends to dominate — add giant danio in a group to spread the pressure.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Giant Danio in a shoal of 6+ or it gets stressed and nippy.
- Giant Glass Catfish⚠️ With cautionPeaceful · 15 cm · Medium care · 22–27 °C (72–81 °F)
- Giant Glass Catfish is slow and long-finned; a busy bucktooth tetra shoal tends to nip at it. Keep bucktooth tetra in a proper group of 8+ and watch them closely.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keyhole Cichlid⚠️ With cautionPeaceful · 10 cm · Easy care · 22–28 °C (72–82 °F)
- Bucktooth Tetra is aggressive and may chase or nip the smaller Keyhole Cichlid — plant heavily and break up sight lines.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Mascara Barb⚠️ With cautionPeaceful · 12 cm · Medium care · 20–25 °C (68–77 °F)
- Expect Bucktooth Tetra to harass Mascara Barb at times; give dense cover and watch them at feeding.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Mascara Barb in a shoal of 8+ or it gets stressed and nippy.
- Molly⚠️ With cautionPeaceful · 10 cm · Easy care · 23–28 °C (73–82 °F)
- Expect Bucktooth Tetra to harass Molly at times; give dense cover and watch them at feeding.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Moonlight Gourami⚠️ With cautionPeaceful · 15 cm · Easy care · 25–30 °C (77–86 °F)
- Bucktooth Tetra is a notorious fin-nipper — even though Moonlight Gourami is larger, an active shoal will harass its trailing fins. Only safe in a full group of 8+ with plenty of cover.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Murray River Rainbowfish⚠️ With cautionPeaceful · 11 cm · Easy care · 15–26 °C (59–79 °F)
- Bucktooth Tetra and Murray River Rainbowfish are close in size, but the aggressive one tends to dominate — add murray river rainbowfish in a group to spread the pressure.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Murray River Rainbowfish in a shoal of 6+ or it gets stressed and nippy.
- Pearl Gourami⚠️ With cautionPeaceful · 12 cm · Medium care · 24–28 °C (75–82 °F)
- Bucktooth Tetra and Pearl Gourami are close in size, but the aggressive one tends to dominate — add pearl gourami in a group to spread the pressure.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Silver Tetra⚠️ With cautionPeaceful · 9 cm · Easy care · 24–28 °C (75–82 °F)
- Bucktooth Tetra is aggressive and may chase or nip the smaller Silver Tetra — plant heavily and break up sight lines.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Keep Silver Tetra in a shoal of 6+ or it gets stressed and nippy.
- Thick-lipped Gourami⚠️ With cautionPeaceful · 9 cm · Easy care · 22–28 °C (72–82 °F)
- Bucktooth Tetra is aggressive and may chase or nip the smaller Thick-lipped Gourami — plant heavily and break up sight lines.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Alligator Gar⛔ Not recommendedAggressive · 250 cm · Hard care · 24–28 °C (75–82 °F)
- Bucktooth Tetra and Alligator Gar are both territorial and at least one is outright aggressive — expect serious fighting.
- Alligator Gar (250 cm) is big enough to swallow the 12 cm Bucktooth Tetra whole.
- Bucktooth Tetra is a notorious fin-nipper — even though Alligator Gar is larger, an active shoal will harass its trailing fins. Only safe in a full group of 8+ with plenty of cover.
- Your 200 L tank is below the ~3785 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Clown Knifefish⛔ Not recommendedAggressive · 90 cm · Hard care · 24–28 °C (75–82 °F)
- Two assertive fish, one genuinely aggressive: Bucktooth Tetra and Clown Knifefish will hold territory and clash.
- Clown Knifefish (90 cm) is big enough to swallow the 12 cm Bucktooth Tetra whole.
- Your 200 L tank is below the ~750 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Fire Eel⛔ Not recommendedSemi-aggressive · 100 cm · Medium care · 24–28 °C (75–82 °F)
- Two assertive fish, one genuinely aggressive: Bucktooth Tetra and Fire Eel will hold territory and clash.
- Size gap is too large (100 vs 12 cm): Fire Eel will treat Bucktooth Tetra as food.
- Your 200 L tank is below the ~380 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Koi⛔ Not recommendedPeaceful · 90 cm · Medium care · 4–28 °C (39–82 °F)
- Bucktooth Tetra is bite-sized to a 90 cm koi — it will be eaten.
- Koi is slow and long-finned; a busy bucktooth tetra shoal tends to nip at it. Keep bucktooth tetra in a proper group of 8+ and watch them closely.
- Your 200 L tank is below the ~3800 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Mekong Giant Catfish⛔ Not recommendedSemi-aggressive · 300 cm · Hard care · 20–28 °C (68–82 °F)
- Bucktooth Tetra and Mekong Giant Catfish are both territorial and at least one is outright aggressive — expect serious fighting.
- Bucktooth Tetra is a notorious fin-nipper — even though Mekong Giant Catfish is larger, an active shoal will harass its trailing fins. Only safe in a full group of 8+ with plenty of cover.
- Your 200 L tank is below the ~100000 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Redtail Catfish⛔ Not recommendedAggressive · 120 cm · Hard care · 24–27 °C (75–81 °F)
- Bucktooth Tetra and Redtail Catfish are both territorial and at least one is outright aggressive — expect serious fighting.
- Redtail Catfish (120 cm) is big enough to swallow the 12 cm Bucktooth Tetra whole.
- Your 200 L tank is below the ~5700 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Spotted Gar⛔ Not recommendedAggressive · 90 cm · Hard care · 18–26 °C (64–79 °F)
- Bucktooth Tetra and Spotted Gar are both territorial and at least one is outright aggressive — expect serious fighting.
- Spotted Gar (90 cm) is big enough to swallow the 12 cm Bucktooth Tetra whole.
- Bucktooth Tetra is a notorious fin-nipper — even though Spotted Gar is larger, an active shoal will harass its trailing fins. Only safe in a full group of 8+ with plenty of cover.
- Your 200 L tank is below the ~600 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ or it gets stressed and nippy.
- Wels Catfish⛔ Not recommendedAggressive · 300 cm · Hard care · 15–25 °C (59–77 °F)
- Bucktooth Tetra and Wels Catfish are both territorial and at least one is outright aggressive — expect serious fighting.
- Size gap is too large (300 vs 12 cm): Wels Catfish will treat Bucktooth Tetra as food.
- Your 200 L tank is below the ~20000 L this pairing really wants — crowding raises aggression.
- Keep Bucktooth Tetra in a shoal of 8+ 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.
Bucktooth Tetra care specs
- Care level
- Medium
- Breeding
- Hard
- Max size
- 12 cm (4.7 in)
- Min tank size
- 200 L (52.8 gal)
- Temperature
- 23–28 °C (73–82 °F)
- pH
- 6–7.5
- Hardness
- 2–12 dGH
- Lifespan
- 5–10 years
- Diet
- Carnivore
- Swim level
- Middle
- Group size
- 8+ (shoaling)
- Family
- Characidae
- Origin
- South America — Amazon and Tocantins river basins, Brazil and Guyana
What is a Bucktooth Tetra?
The bucktooth tetra (Exodon paradoxus) is one of the freshwater hobby’s most striking and notoriously aggressive characids. Native to the Amazon and Tocantins river basins of Brazil and Guyana, it reaches up to 12 cm (nearly 5 in) and is immediately unmistakable: a polished silver body marked by two large, solid black spots — one below the dorsal fin and one at the caudal peduncle — with vivid red-orange coloration blazing at the tips of the dorsal and caudal fins. In a large school under bright lighting, the effect is genuinely dazzling.
The common name is no exaggeration. Bucktooth tetras are specialist lepidophages — scale-eaters — that use protruding, outward-angled teeth to tear scales and tissue from other fish. This is hardwired behaviour that satiation does not suppress; it is simply what they are. That reality makes them an expert-level fish, not a community tank fish, and keepers who accept that upfront are rewarded with one of the most dynamic shoaling spectacles available in freshwater aquariums.
Where do Bucktooth Tetras come from?
Exodon paradoxus is found across the middle and lower Amazon basin and the Tocantins drainage in Brazil, with additional records from Guyana. Wild populations inhabit warm, moderately flowing rivers and streams with soft, slightly acidic water. These systems carry significant tannin staining from submerged leaf litter and wood, which buffers pH and keeps hardness low.
Understanding this origin matters for husbandry. The fish are adapted to water that is warm, soft and gently acidic — not the harder, alkaline tap water found in many regions. Conditioning water before use, or blending with RO water, helps replicate their natural range and tends to improve coloration and long-term health.
What Tank Setup and Size do Bucktooth Tetras Need?
A bare minimum of 200 litres (55 gallons) is required for a starter group of eight bucktooths — and that should be treated as a floor, not a target. The species is a fast, open-water swimmer that uses the full horizontal length of the tank; a long footprint (120 cm / 48 in or more) is far preferable to a tall, narrow aquarium.
The ideal layout gives the fish a large, unobstructed swimming zone in the centre and mid-section, with structured cover at the edges and ends: robust plants such as java fern, anubias or large-leaved Amazon swords, along with pieces of driftwood and rounded rocks. Bucktooths will not eat live plants but they will bulldoze delicate stem plants during their constant, purposeful swimming. Use a robust external canister filter sized for the tank volume — good turnover matters, but avoid a current so strong it exhausts the fish. A tight-fitting lid is essential; they are capable jumpers.
For those wanting to keep a more impressive group of 15–20 individuals, a 300 L (80 gal) or larger tank becomes appropriate. Counter-intuitively, a larger school is often more stable — intra-group posturing is spread across more fish, and no single individual takes a disproportionate share of aggression.
What Water Parameters do Bucktooth Tetras Need?
- Temperature: 23–28 °C (73–82 °F). A reliable heater with a thermometer is essential.
- pH: 6.0–7.5. They tolerate a reasonably wide range, but the softer and more acidic end of their range reflects their natural origin.
- Hardness: 2–12 dGH. Soft to moderately hard water suits them well; avoid very hard, high-mineral water.
As with most tropical fish, stability matters more than hitting exact numbers. A well-cycled tank with consistent weekly water changes of 25–30% keeps nitrates in check and prevents the parameter swings that stress fish and open the door to disease. Use a dechlorinator appropriate for your tap water, and allow the tank to mature fully before adding fish.
What do Bucktooth Tetras Eat?
Bucktooth tetras are dedicated carnivores, and their diet in the aquarium should reflect that. A varied menu of high-quality foods keeps them in good condition and, to a degree, reduces the intensity of scale-raiding behaviour directed at tankmates when they are kept with other species (though they should not be).
Good staple choices include quality sinking or floating carnivore pellets and sticks. Supplement regularly with frozen foods: bloodworms, white mosquito larvae, daphnia, brine shrimp, small prawns and silversides all work well. Live foods such as ghost shrimp or feeder guppies can be offered occasionally, though this carries disease-introduction risks unless the feeder stock is reliably sourced. Avoid large amounts of plant-based foods — these fish have no need for them and will ignore most vegetable matter.
Feed once or twice a day, offering only what the group consumes within a few minutes. Overfeeding degrades water quality rapidly, especially in a densely stocked carnivore tank.
What is the Behaviour and Compatibility of Bucktooth Tetras?
The bucktooth tetra’s aggression is not situational — it is the species’ defining trait. They are specialist scale-eaters, and almost any fish sharing their aquarium will eventually be harassed, stripped of scales or killed. This applies to fish far larger than themselves; they hunt cooperatively and are bold enough to attack fish several times their size.
The only reliable approach is a single-species tank of eight or more individuals. At that group size, the fish’s social energy is primarily directed inward — constant posturing, mock-chasing and competitive feeding among themselves produces the spectacular churning-school behaviour the species is known for. Below eight, weaker fish are targeted relentlessly and may be killed. Paradoxically, the larger the group, the more evenly aggression is distributed and the more stable the school becomes.
Invertebrates and snails will be eaten or harassed. Adding any other fish species, even “armoured” fish like plecos, is generally inadvisable and should only be attempted by experienced keepers with a backup tank ready.
For a full assessment of compatible species — including the very short list of fish occasionally kept alongside bucktooths under controlled conditions — see Bucktooth Tetra tank mates.
How do you Tell Male and Female Bucktooth Tetras Apart?
Sexual dimorphism in Exodon paradoxus is minimal. The frontmatter notes it plainly: females become slightly fuller-bodied through the abdomen when gravid (carrying eggs), but outside of that breeding condition the sexes are nearly identical in finnage, coloration and size. This makes reliable sexing of individual fish difficult in normal display conditions.
Experienced keepers buying a group of eight or more are likely to end up with a mix of both sexes by chance, which is the practical approach. There is no external marker comparable to the egg spot found in many cichlids or the fin differences found in livebearers that allows confident individual sexing at a glance.
How do Bucktooth Tetras Breed?
Breeding Exodon paradoxus in captivity is hard — and that rating is well-earned. Spawning itself is an egg-scattering event typical of many characins; a conditioned pair or small group will scatter adhesive eggs among fine-leaved plants or a spawning mop, then promptly eat them if not removed.
A successful attempt requires a dedicated breeding tank separate from the display, pairs or trios conditioned on a varied live and frozen diet, and very soft, warm, slightly acidic water toward the lower end of their parameter range. Eggs are reported to hatch within 24–48 hours at around 27 °C (81 °F). Raising fry adds another layer of difficulty: they are tiny and require infusoria or commercial fry foods initially, graduating to micro-worms and baby brine shrimp as they grow. Adult bucktooths will eat their own young without hesitation. Captive breeding remains relatively rare and is a project for experienced breeders rather than a likely outcome in a standard display tank.
What are Common Bucktooth Tetra Diseases?
Bucktooth tetras kept in warm, soft, stable and well-maintained water are reasonably hardy. The diseases most commonly encountered are those that affect tropical freshwater fish broadly: ich (Ichthyophthirius multifiliis, visible as white salt-grain spots), fin rot (ragged or receding fin edges linked to bacterial infection and usually triggered by water-quality failure), and internal parasites, which are worth guarding against particularly in wild-caught stock.
The most effective prevention is straightforward:
- Maintain a fully cycled tank with stable parameters and regular water changes.
- Quarantine all new fish for a minimum of four weeks in a separate tank before introducing them.
- Feed a varied, high-quality diet to keep immune function strong.
- Remove uneaten food promptly to avoid ammonia spikes.
Health note: diagnosing disease accurately before medicating is important — many medications stress fish and harm biological filtration. For sick fish, identify symptoms carefully against a reputable veterinary or fish-health source before reaching for a treatment.
How Long do Bucktooth Tetras Live?
A well-kept bucktooth tetra lives 5–10 years in captivity. That range reflects variation in individual fish and in the quality of husbandry — a stable, appropriately sized tank with good water quality, a varied diet and a large enough group to allow natural social behaviour puts fish squarely at the longer end of that lifespan.
Much of the stock seen in the hobby is wild-caught, so the age of fish at purchase is often unknown. Buying from a reputable source, quarantining new arrivals and investing in a large enough tank from the start are the decisions that most directly determine how long and how well these remarkable fish do in your care.
Frequently asked questions
Can bucktooth tetras live with other fish?
Rarely. They are specialist scale-eaters that will strip fins and scales from virtually any companion. The only reliable approach is a large, single-species school of eight or more — redirecting aggression among themselves keeps individuals safer and produces their most impressive shoaling display.
How big a tank do bucktooth tetras need?
At minimum 200 litres (55 gallons) for a school of eight, and larger is always better. They are fast, open-water swimmers that use the full length of the tank. A 300 L+ tank lets you keep a more impressive group of 15–20.
What you need to keep a bucktooth tetra
The baseline is a heated, filtered 200 L+ tank: a reliable heater to hold 23–28 °C (73–82 °F), a gentle filter that won't batter a bucktooth tetra in the current, and a tight-fitting lid. Cycle the tank fully before adding any fish.
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