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No federal permit to keepFlag tetra
Hyphessobrycon heterorhabdus
Fishes › Tetras, piranhas and pacus (Characiformes) › Characidae (Tetras)
Hyphessobrycon heterorhabdus, the flag tetra or Belgian flag tetra, is a species of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins.
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 1.4 in / 3.56 cm).
- Water: Freshwater.
- Temperature: 73–82°F (range recorded for this species).
- pH: 5.5–7.5.
- Hardness: 0–15 dGH.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Diet: Eats a varied diet: mix quality prepared foods with frozen and live foods. FishBase classes it as a omnivore.
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 31 × 12 in (roughly 19 US gallons); space needed is rated “modest tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 68–79 °F, pH 5.5–7.5, 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: “Perhaps looks best in an arrangement comprising a sandy substrate plus some driftwood roots and branches, or heavily-planted planted set-up.”
- Diet: “Likely to be omnivorous feeding on small invertebrates, crustacea, filamentous algae, fallen fruit and suchlike in nature.”
- Tankmates: “Very peaceful making it an ideal resident of the well-researched community aquarium.”
- Breeding: “An egg-scattering free spawner exhibiting no parental care.”
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 distinguished by its vibrant coloration and patterns, which have contributed to its popularity in the aquarium trade.
Quoted from the Wikipedia article “Hyphessobrycon heterorhabdus” (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. Uses both the bottom and open water. Feeds on worms, crustaceans and plant matter. |
| Water it lives in | Freshwater, 73–82 °F (23–28 °C), pH 5.5–7.5, hardness 15 dH. |
| Climate | Tropical climate. |
| 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 90°F (up to 92°F in the hottest sampled areas) |
| Cool-season lows | about 69°F (down to 61°F in the coldest sampled areas) |
| Average temperature | 77–80°F across sampled records |
| Relative humidity | 80–83% on average (driest month about 76%) |
| Rainfall | about 2236 mm a year |
Measured at 113 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 | Hyphessobrycon heterorhabdus, the flag tetra or Belgian flag tetra, is a species of freshwater ray-finned fish belonging to the family Acestrorhamphidae, the American characins. This fish is distinguished by its vibrant coloration and patterns, which have contributed to its popularity 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 |
| Wild diet | The diet of Hyphessobrycon heterorhabdus predominantly consists of small invertebrates and plant matter. In their natural habitat within the Amazon Basin, these fish adapt to a varied diet that includes micro-crustaceans, worms, small insects, and detritus, reflecting the rich biodiversity of their ecosystem. — Wikipedia (community-edited) |
| Reproduction | Breeding Hyphessobrycon heterorhabdus in captivity involves creating conditions that mimic their natural habitat, particularly the rainy season of the Amazon Basin. A dedicated breeding tank with soft, acidic water (pH 6.0 to 6.5), a temperature of around 24°C (75°F), dim lighting, and fine-leaved plants or spawning mops can encourage spawning. — Wikipedia (community-edited) |
| Appearance and size | Hyphessobrycon heterorhabdus exhibits a distinctively elongated and laterally compressed body shape, characteristic of many species within the characin family. One of its most striking features is its vividly red-colored eyes, which contrast sharply with its overall body coloration. Along its lateral line, the fish displays a prominent stripe that integrates black, red, and yellow lines. — Wikipedia (community-edited) |
| Biology | Feeds on worms, crustaceans and plant matter. — FishBase |
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 total length. Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 31 × 12 in (about 19 US gallons).
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.
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