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Hemiodus gracilis, also known as the Red Hockeystick Tetra, is a slender Amazonian characin recognized by its silvery body and reddish lower fins. Its profile resembles a small curved stick, which explains its English name. This is a peaceful schooling fish that should be kept in a group in a mature, well-oxygenated aquarium. Collected from the wild, it is considered moderately rare in the aquarium trade. It is also exclusive to Ton.Fish in Canada.

General description of the species

Hemiodus gracilis is a small freshwater fish from the family Anostomidae, adapted to life in groups in tropical South American waterways. It usually remains in open water or in the middle levels of the aquarium, swimming with continuous and coordinated movements. Its temperament is peaceful, although it appreciates enough space to express its natural activity. A group of at least six individuals helps reduce nervousness and encourages more natural behavior. The species is suitable for a community aquarium with calm tank mates. Its rarity level 2 makes it less common than many popular Amazonian tetras. Efficient filtration, stable water and good oxygenation are recommended, especially for wild-collected specimens.

Geographical origin and biotope

Reference country: Brazil. Hemiodus gracilis is associated with the Amazon Basin, particularly the Rio Negro drainage. Its natural habitat consists of tropical freshwater environments often tinted by organic material from the surrounding forest. These habitats usually have subdued light, low mineral content and an abundance of branches, roots and leaf litter. In an aquarium, driftwood, suitable leaves and vegetation around the edges can recreate this setting without filling the entire swimming area. Slightly acidic to neutral water and a stable tropical temperature suit its maintenance. Moderate lighting helps reveal its silvery and reddish tones.

Precise location and local name

The aquarium distribution of Hemiodus gracilis primarily associates it with the Rio Negro and its tributaries in northern Brazil. It occurs in forested areas where the banks contribute plant debris and light reaches the water only diffusely. The English trade name Red Hockeystick Tetra is the easiest way to distinguish it in the specialty trade. In French, the name Hemiodus gracilis is the most direct designation. Wild-collected fish may require careful acclimation, particularly when moved into harder or brightly lit water. A quarantine period remains a useful precaution before introducing them to the main aquarium.

Appearance and physical characteristics

The body of Hemiodus gracilis is slim, elongated and laterally compressed, with a gently arched dorsal profile. The base color is silvery, with a sheen that changes according to lighting and the fish’s condition. The lower fins display red to orange tones, especially in healthy specimens. Its body shape and posture resemble a small stick, which explains the hockeystick reference in its English name. The mouth is terminal to slightly forward-facing, suited to taking small particles from the water column and near surfaces. Adults reach approximately 10 cm under good conditions, so an aquarium with a useful length of open swimming space is recommended.

General diet

In the aquarium, Hemiodus gracilis generally accepts quality dry foods such as micro pellets and fine flakes, as well as frozen foods. A varied diet including brine shrimp, daphnia and small meaty foods helps maintain condition and color intensity. Vegetable ingredients, offered through tablets or foods containing algae, can complement the ration because the species benefits from a diverse diet. Small portions should preferably be offered once or twice daily, while ensuring that every fish can feed. Wild specimens may take several days to accept prepared foods. Variety and consistency are more important than relying on one particularly rich food.

Essential data

• River of origin: Rio Negro
• Local name used: Red Hockeystick Tetra
• Origin of the scientific name: Hemiodus is a Greek-derived genus name associated with the idea of half-tooth; gracilis describes the fish’s slender and delicate form.
• Etymology of the full name: Hemiodus approximately means half-tooth, while gracilis means slender, graceful or delicate.
• Common/vernacular names: Red Hockeystick Tetra; red hockeystick tetra
• Family: Anostomidae
• Subfamily: Anostominae
• Name pronunciation: hee-mee-OH-duss - grah-SILL-iss
• Discovery: Albert Carl Ludwig Gotthilf Günther, 1866
• Maximum adult size: Approximately 10 cm
• Water temperature and pH: 24 to 28 °C; pH 5.5 to 7.0
• Watercourse appearance and surrounding vegetation: Shaded forest waters often tinted by organic matter, with roots, branches, leaf litter and dense riparian vegetation.
• Typical tank mates: Paracheirodon axelrodi, Hemigrammus rhodostomus, Nannostomus eques, small corydoras and other peaceful characins.
• Temperament and behavior: Peaceful, schooling and active; it should be kept in groups of at least six individuals.
• Water depth: Middle levels of waterways and calm to moderately flowing areas.
• Sexual dimorphism: Limited; mature females may have a rounder abdomen.
• Bottom structure and flow: Sandy or fine substrate, plant debris, roots and low to moderate flow with good oxygenation.

In your aquarium

To successfully keep Hemiodus gracilis, choose a mature, elongated aquarium with a secure cover, roots, subdued lighting and open swimming areas. Keep it in a group and avoid aggressive or much larger tank mates that could intimidate it. Stable, clean and well-oxygenated water is essential, especially for wild-collected fish. A varied diet, regular water changes and gradual acclimation support longevity and coloration. Under these conditions, this peaceful schooling tetra becomes a striking part of a balanced Amazonian community or biotope aquarium.