Thoracocharax stellatus

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Thoracocharax stellatus, also known as the Silver Hatchetfish, is a small South American surface-dwelling fish valued for its unusual body shape and schooling behavior. Its laterally compressed body, deeply arched belly, and high-set pectoral fins give it a distinctive appearance. Native to the Orinoco basin, including Colombia, it inhabits calm or moderately flowing waters bordered by vegetation. These areas provide shade, cover, and access to insects that fall onto the water’s surface. The species is naturally collected in the wild and remains moderately uncommon in the aquarium trade. It requires a tightly covered aquarium, stable water conditions, and a varied floating diet.

General species description

Thoracocharax stellatus is a freshwater hatchetfish specialized for life near the surface. It is peaceful, social, and especially interesting to watch when moving as a group beneath the waterline. It mainly occupies the upper part of the aquarium and benefits from open swimming space combined with floating plants. Like many hatchetfish, it may leap when startled, so a securely fitted lid is essential. It is best suited to a calm community aquarium rather than a highly turbulent setup or a tank containing aggressive fish. The species is naturally collected in the wild, and its availability is moderate rather than consistently high among specialized retailers.

Geographic origin and biotope

The species is associated with the Orinoco basin in South America, with Colombia as the reference country. It inhabits lowland areas where the water may be fairly calm, including margins, smaller channels, and areas influenced by overhanging vegetation. These habitats provide a steady supply of terrestrial insects and visual shelter near the surface. Light is often softened by floating plants, branches, or dense bankside growth. In the aquarium, this translates into a preference for warm, soft to moderately mineralized water ranging from slightly acidic to neutral. Efficient filtration without harsh turbulence more closely reflects the conditions favored by Orinoco surface fishes.

Specific location and local name

Information used in the aquarium trade places Thoracocharax stellatus in Colombia and the Orinoco basin. The English common name Silver Hatchetfish is the most practical name when dealing with suppliers. The French translation poisson-hachette argenté may also be encountered, although commercial usage varies by region and importer. A precise Indigenous or regional vernacular name is not included here. To avoid confusion, it is best to request the complete scientific name, Thoracocharax stellatus, rather than relying only on Silver Hatchetfish, a name that may be applied broadly to several silvery hatchetfish species.

Appearance and physical characteristics

The body of Thoracocharax stellatus is short, deep, and strongly compressed from side to side. Its most notable feature is the very deep hatchet-shaped belly, combined with a comparatively straight dorsal profile. The overall coloration is silvery, with a metallic sheen that blends with the light near the surface. The pectoral fins are set high on the body and help the fish make rapid leaps from the water; they should not, however, be interpreted as providing sustained flight. The mouth points upward, matching its surface-feeding lifestyle. Adult size remains small, allowing a group to be kept in a suitably long, tightly covered aquarium.

General diet

In nature, Thoracocharax stellatus feeds mainly on small prey available at the surface, especially terrestrial insects and other small organisms. In the aquarium, it accepts floating foods such as small granules, flakes that remain at the surface, and appropriately sized freeze-dried foods. Frozen foods, including mosquito larvae or daphnia, can add variety. Feed small portions because its upturned mouth and surface-oriented behavior make it less effective at recovering food that sinks to the bottom. A varied diet supports good condition and coloration. Watching feeding response helps ensure that more timid individuals also receive enough food.

Essential data

• River of origin: Orinoco basin
• Local name used: Silver Hatchetfish
• Origin of the scientific name: Thoracocharax is the genus name; stellatus is the specific epithet.
• Full-name etymology: Thoracocharax refers to the chest or thorax and the Greek term charax, associated with a fish or pointed form; stellatus means starry.
• Common/vernacular names: Silver Hatchetfish; poisson-hachette argenté
• Family: Gasteropelecidae
• Subfamily: no commonly used subfamily
• Name pronunciation: thor-ack-oh-KAR-aks - stell-AH-tus
• Discovery: Rudolf Kner, 1858
• Maximum adult size: approximately 6 cm
• Water temperature and pH: 24 to 28 °C; pH 5.5 to 7.5
• Watercourse appearance and surrounding vegetation: calm to moderately flowing water, shaded margins, bankside vegetation, and floating plants
• Typical tankmates: peaceful small tetras, small corydoras, pencilfish, small loricariids, adult shrimp, and other calm surface fish
• Temperament and behavior: peaceful, schooling, active near the surface, and capable of jumping
• Water depth: shallow surface zones along margins and channels
• Sexual dimorphism: difficult to determine; mature females may be fuller-bodied
• Bottom and current: sandy or muddy substrate with plant debris; low to moderate current

For aquarium success

To keep Thoracocharax stellatus successfully, choose a long aquarium with a secure cover and floating plants that soften the lighting without completely blocking the surface. Keep it in a group and avoid boisterous or predatory tankmates. Warm, stable, clean water is essential, together with filtration that produces gentle movement. Offer small portions of varied floating foods on a regular schedule. Because this species is naturally collected in the wild and moderately uncommon in the trade, careful acclimation and a thorough quarantine are especially sensible.