Home / Fishes / Tetras, piranhas and pacus / Bucktooth tetra
No federal permit to keepBucktooth tetra
Exodon paradoxus
Fishes › Tetras, piranhas and pacus (Characiformes) › Characidae (Tetras)
The bucktooth tetra (Exodon paradoxus) is a species of freshwater ray-finned fish, a characin, belonging to the family Characidae.
Care at a glance
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 3.0 in / 7.5 cm).
- Water: Freshwater.
- Temperature: 73–82°F (range recorded for this species).
- pH: 5.5–7.5.
- Hardness: 0–20 dGH.
- Layout: An open-water swimmer: needs long, open swimming space with few obstacles.
- Diet: A predator: feed meaty foods sized to its mouth (frozen fish, shrimp, worms); it will eat tankmates that fit in its mouth. FishBase classes it as a carnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 47 × 18 in (roughly 64 US gallons); space needed is rated “large tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 73–82 °F, pH 5.5–7.5, 0–20 dGH.
- Behaviour: a shoaling fish best kept in a group of six or more.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “A biotope setup would consist of a substrate of sand with perhaps a few driftwood branches and roots added for effect.”
- Diet: “Gut analyses of wild specimens have shown that the diet consists largely of insects and the scales of other fish.”
- Tankmates: “This is not a community fish, and is best kept in a species setup.”
- Breeding: “Has been achieved, albeit rarely.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Tetras
Applies to most species in this group. Habitat: The covered characids include South American river and tributary fishes, from vegetation-shaded bloodfin habitats to sandy flowing rivers occupied by Exodon. [fg156-bloodfin, fg156-exodon]. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- For glass bloodfins, use at least 60 × 38 × 30 cm (24 × 15 × 12 in), retaining open upper-water swimming space.
- Provide planted margins and floating vegetation for bloodfins; fit a tight lid for Aphyocharax anisitsi.
- For bucktooth tetras use at least 120 × 45 × 45 cm (48 × 18 × 18 in), efficient filtration and planted refuges from bullying.
- For glass bloodfins maintain pH 6.0–7.5; for Exodon, pH 5.5–7.5.
Climate & lighting
| Water | 73.4–80.6°F |
Diet
- Small dried foods for glass and ordinary bloodfins.
- Daphnia, Cyclops and bloodworms for glass bloodfins.
- For Exodon, chopped prawns, mussels, earthworms and fish rather than live feeder fish.
Social life
- Glass bloodfins need 6–8 or more; ordinary bloodfins at least six. Exodon requires a species aquarium and at least 12 introduced together; small groups can kill one another.
Health watch
- Freshwater ich (white spot disease), a general aquarium risk.
- Bacterial infections associated with stress and poor water quality.
- Fin and scale damage from aggression, especially Exodon.
Understanding the animal
About this animal
About this animal
This fish is found in South America. It is the only species in the monospecific genus Exodon.
Quoted from the Wikipedia article “Bucktooth tetra” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater. |
| Water it lives in | Freshwater, 73–82 °F (23–28 °C), pH 5.5–7.5, hardness 20 dH. |
| Climate | Tropical climate. |
| Wild diet | Hunting macrofauna (predator). |
| Behavior to plan for | Breeding: open water/substratum egg scatterers. |
What this means for care
- Keep water within its wild range, 73–82 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 93°F (up to 95°F in the hottest sampled areas) |
| Cool-season lows | about 68°F (down to 60°F in the coldest sampled areas) |
| Average temperature | 77–82°F across sampled records |
| Relative humidity | 74–79% on average (driest month about 65%) |
| Rainfall | about 1786 mm a year |
Measured at 104 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | The bucktooth tetra (Exodon paradoxus) is a species of freshwater ray-finned fish, a characin, belonging to the family Characidae. This fish is found in South America. It is the only species in the monospecific genus Exodon. The bucktooth tetra occasionally turns up in the aquarium trade. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Appearance and size | The bucktooth tetra has an elongated, laterally compressed body and a forked caudal fin. It attains a maximum standard length of 7.5 cm. There is a black line which extends from the operculum to the caudal peduncle; this joins two black blotches, one near the middle of the body and the other near the caudal peduncle. — Wikipedia (community-edited) |
| Biology | The bucktooth tetra is a shoaling fish which is mainly lepidophagous, feeding on the scales of other fishes, with fish sampled from the wild having 88% of their diet made up of fish scales, 10% of insects and other animal matter, and a tiny amount of plant material. The scale feeding habit has led these fishes to develop handedness. Each fish always approaches their intended victim from a favoured side. — Wikipedia (community-edited) |
| History and naming | The bucktooth tetra was first formally described, as Exodon paradocus, in 1844 by the German zoologists Johannes Peter Müller and Franz Hermann Troschel, with its type locality given as the Essequibo River in Guyana. When Müller and Troschel described this species, they classified it in a new monospecific genus, Exodon. — Wikipedia (community-edited) |
| Conservation | The bucktooth tetra is assessed to be Least Concern by the International Union for Conservation of Nature because it has a wide distribution and is common throughout that distribution. — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Adult length
Maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Minimum tank footprint
Seriously Fish recommends a tank base of at least 47 × 18 in (about 64 US gallons).
Veterinary & husbandry research
Veterinary & husbandry research
- Jaw laterality and related handedness in the hunting behavior of a scale-eating characin, Exodon paradoxus Hata H et al., PloS one 2011
Peer-reviewed papers that mention this species alongside captivity, zoos, veterinary care or aquaculture. Some cover several species or mention it only in passing, so check the abstract. 170
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Seriously Fish: Prionobrama filigera Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish: Exodon paradoxus Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish: Aphyocharax anisitsi Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Merck Veterinary Manual: Disorders and Diseases of Fish Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- PubMed (U.S. National Library of Medicine) Peer-reviewed researchIndex of peer-reviewed veterinary, zoo and husbandry research.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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