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Hemigrammus filamentosus, also known as the Phoenix Tetra, is a small South American characin valued for its delicate appearance and schooling behavior. Its translucent body, silvery reflections, and finely shaped fins create an attractive display in a planted aquarium. Like many Amazonian tetras, it should be kept in a group and offered stable, soft to moderately acidic water. This species suits peaceful community aquariums, where it usually occupies the middle levels. A varied diet, subdued lighting, and abundant vegetation help bring out its natural appearance and encourage confident, coordinated movements.

General species description

Hemigrammus filamentosus is a small freshwater tetra in the family Characidae. It is a schooling fish that feels more secure in a group; keeping about eight or more individuals encourages natural behavior and reduces shyness. In an aquarium, it mainly swims through the middle levels, showing quick but generally peaceful movements. Its temperament suits a community aquarium containing calm fish of similar size. The species benefits from clean, well-oxygenated water and consistent maintenance. It is generally available through the aquarium trade, making it accessible to aquarists looking for a small Amazonian characin that is less familiar than the most common tetra species.

Geographical origin and biotope

Country of reference: Brazil. Hemigrammus filamentosus is associated with the Rio Tapajós basin in north-central Brazil. Its natural environment consists of tropical forest streams, where the canopy and riverbank vegetation often filter sunlight. The habitat may include branches, roots, leaf litter, and quiet areas along the margins. The water is generally soft and slightly acidic to neutral, with warm temperatures and limited sudden changes. In an aquarium, a dark substrate, plants, wood, and shaded areas help recreate this setting and make the fish’s schooling behavior easier to observe.

Precise location and local name

The reference distribution of Hemigrammus filamentosus is in the Rio Tapajós basin of Brazil. The most commonly used trade name is Phoenix Tetra. No widely established Brazilian vernacular name is retained for aquarium use. Because small tetras can be confused with one another in the trade, identification should ideally rely on the complete scientific name and the origin provided by the supplier. When selecting fish, choose active specimens with intact fins, normally filled bellies, and coordinated schooling behavior. A gradual acclimation is important, especially when the arrival water differs greatly from the aquarium water.

Appearance and physical characteristics

Hemigrammus filamentosus has an elongated, laterally compressed body with an overall silvery and translucent appearance. Its delicate fins contribute to its light, refined profile, while mature males may show more developed fins and a slimmer body shape. The specific name filamentosus refers to a filamentous or elongated feature of some fin rays. Color intensity can change with mood, lighting, age, and water quality. A planted aquarium with a dark background and moderate lighting often improves visual contrast. It is still best not to confuse this fish with other small tetras that have a similar body shape.

General feeding

Hemigrammus filamentosus is an opportunistic omnivore that accepts a varied diet of small dry foods, frozen foods, and live foods. High-quality flakes or micro-pellets can form the basis of its diet, supplemented with baby brine shrimp, daphnia, or small worms suitable for its mouth. Small portions offered once or twice daily help limit waste and allow all fish to feed. A varied diet supports body condition and color expression. Food items should be appropriately sized, since pieces that are too large are difficult for this small characin to eat.

Essential data

• River of origin: Rio Tapajós
• Local name used: Phoenix Tetra
• Origin of the scientific name: Hemigrammus is the genus name; filamentosus describes a filamentous or elongated feature.
• Etymology of the full name: Hemigrammus approximately means “half-line,” referring to a body mark or line; filamentosus means “filamentous.”
• Common/vernacular names: Phoenix Tetra
• Family: Characidae
• Subfamily: —
• Name pronunciation: hem-ee-GRAM-us - fil-am-en-TOE-sus
• Discovery: Axel Zarske, 2017
• Maximum adult size: About 4 cm
• Water temperature and pH: 24 to 28 °C; pH 5.5 to 7.0
• Stream appearance and surrounding vegetation: Tropical forest streams, often shaded, with branches, roots, leaf litter, and riverbank vegetation.
• Typical tankmates: Hemigrammus rhodostomus, Paracheirodon axelrodi, Hoplisoma panda
• Temperament and behavior: Peaceful, social, and active; keep in a group.
• Water depth: Shallow to intermediate sections of streams.
• Sexual dimorphism: Females are often rounder; males are generally slimmer and may have more developed fins.
• Bottom structure and flow: Sandy or fine substrate, plant debris, and low to moderate flow.

In your aquarium

To succeed with Hemigrammus filamentosus, use a mature, well-filtered aquarium furnished with dense plants, wood, and shaded areas. Keep it in a group and avoid aggressive tankmates or fish that are much larger. A stable tropical temperature, slightly acidic to neutral water, and small varied meals will support good condition. Regular water changes, daily observation, and careful acclimation complete the key requirements for keeping this species successfully in an aquarium.