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No federal permit to keepCardinal tetra
Paracheirodon axelrodi
Fishes › Tetras, piranhas and pacus (Characiformes) › Characidae (Tetras)
The cardinal tetra (Paracheirodon axelrodi) is a species of freshwater fish of the family Acestrorhamphidae, the American characins, of order Characiformes.
Care at a glance
Species-specific values
Values researched for this exact species. Where they differ from the group guide below, follow these. Air, surface and water temperatures are listed separately, and each source is kept as published rather than averaged.
| Water temperature | 73–84 °F (23–29 °C) Maintenance recommendations from this source; do not replace with a multisource average. | 249 |
| Water pH | 3.5–7.5 Maintenance recommendations from this source; do not replace with a multisource average. | 249 |
| Water general hardness | 1–12 dGH Maintenance recommendations from this source; do not replace with a multisource average. | 249 |
| Adult standard length | 35 mm Maximum standard length reported by source; excludes caudal fin, not total body length. | 249 |
| Minimum tank base | length: 60 cm; width: 30 cm Minimum aquarium base recommended by this source, not a tank-volume specification. | 249 |
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 1.0 in / 2.51 cm).
- Water: Freshwater.
- Temperature: 73–81°F (range recorded for this species).
- pH: 4–6.
- Hardness: 5–12 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 24 × 12 in (roughly 14 US gallons); space needed is rated “modest tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 73–84 °F, pH 3.5–7.5, 1–12 dGH.
- Behaviour: temperament peaceful; a shoaling fish best kept in a group of six or more; suited to a community tank.
- Difficulty: Easy (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Maintenance generally presents few problems although a degree of care is necessary with wild specimens which are more intolerant of deteriorating water conditions than commercially-produced fish.”
- Diet: “Likely to be omnivorous feeding on small invertebrates, crustacea, filamentous algae, fallen fruit and suchlike in nature.”
- Tankmates: “Generally peaceful making it an ideal resident of the well-researched community aquarium.”
- Breeding: “You'll need to set up a dedicated tank if you want to raise decent numbers of fry.”
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
It is native to the upper Orinoco and Negro Rivers in South America. Growing to about 3 cm (1.2 in) in total length, the cardinal tetra has the striking iridescent blue line characteristic of the genus Paracheirodon laterally bisecting the fish, with the body below this line being vivid red in color, hence the name "cardinal tetra".
Quoted from the Wikipedia article “Cardinal 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. Occurs mainly in shoals in the middle water layers. Feeds on worms and small crustaceans. |
| Water it lives in | Freshwater, 73–81 °F (23–27 °C), pH 4–6, hardness 5–12 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, 73–81 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 90°F (up to 95°F in the hottest sampled areas) |
| Cool-season lows | about 70°F (down to 69°F in the coldest sampled areas) |
| Average temperature | 79–81°F across sampled records |
| Relative humidity | 79–85% on average (driest month about 80%) |
| Rainfall | about 2553 mm a year, spread fairly evenly |
Measured at 73 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 cardinal tetra (Paracheirodon axelrodi) is a species of freshwater fish of the family Acestrorhamphidae, the American characins, of order Characiformes. It is native to the upper Orinoco and Negro Rivers in South America. Growing to about 3 cm in total length, the cardinal tetra has the striking iridescent blue line characteristic of the genus Paracheirodon laterally bisecting the fish, with the body below this line being vivid red in color, hence the name "cardinal tetra". — 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 |
| Social life and communication | Communication has not been described in this species. — Animal Diversity Web |
| Wild diet | The diet of P. axelrodi consists of very small crustaceans, mesofauna, eggs, algae, detritus, and some other types of prey. — Animal Diversity Web |
| Behavior | Paracheirodon axelrodi individuals are active during the day, and live in schools of several thousands in natural habitats. — Animal Diversity Web |
| Reproduction | Female cardinal tetras release their eggs during the rainy season. — Animal Diversity Web |
| Lifespan | Cardinal tetras are able to live longer in captivity than in the wild. — Animal Diversity Web |
| Appearance and size | Cardinal tetras are small fish, males grow to about 2.5 cm in length in the wild, but can attain lengths of 5 cm in an aquarium. — Animal Diversity Web |
| Biology | Occurs mainly in shoals in the middle water layers. Feeds on worms and small crustaceans. Breeding in captivity is possible but difficult and most specimens in the aquarium trade are caught in the tributaries of the Rio Negro and Orinoco. — FishBase |
| History and naming | American ichthyologist Leonard Peter Schultz described the cardinal tetra in 1956 as Cheirodon axelrodi. The specific epithet honors fishkeeping book publisher Herbert R. Axelrod. Hyphessobrycon cardinalis is an obsolete synonym. — Wikipedia (community-edited) |
| Conservation | Cardinal tetras are common in their native range, they are not considered threatened. — Animal Diversity Web |
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 24 × 12 in (about 14 US gallons).
Veterinary & husbandry research
Veterinary & husbandry research
- Ichthyological ethnoknowledge of the "piabeiros" from the Amazon region, Brazil da Silva Ladislau D et al., Journal of ethnobiology and ethnomedicine 2021
- Parasites of ornamental fish commercialized in Macapá, Amapá State (Brazil) Hoshino ÉM et al., Revista brasileira de parasitologia veterinaria = Brazilian journal of veterinary parasitology: Orgao Oficial do Colegio Brasileiro de Parasitologia Veterinaria 2018
- Tetra disseminated microsporidiosis: a novel disease in ornamental fish caused by Fusasporis stethaprioni n. gen. n. sp Lovy J et al., Parasitology research 2021
- Mechanisms of Na+ uptake, ammonia excretion, and their potential linkage in native Rio Negro tetras (Paracheirodon axelrodi, Hemigrammus rhodostomus, and Moenkhausia diktyota) Wood CM et al., Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology 2014
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. See all 5 on PubMed → 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.
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