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Potamorraphis guianensis, also known as Needle Fish, is a freshwater fish with a remarkably slender profile. Its narrow body and elongated mouth give it an immediately recognizable appearance among South American fishes. Native to the aquatic environments of the Guianas region, it inhabits calm or moderately flowing areas where it can remain close to the surface. This species has an intermediate level of rarity in the specialized trade and is generally offered as a wild-collected fish. It is best suited to aquarists who can maintain stable, well-oxygenated water and a quiet aquarium environment.

General species description

Potamorraphis guianensis is a freshwater fish in the order Beloniformes, adapted to life mainly in open water and near the surface. Its body shape resembles that of needlefish: slender, fusiform and extended by a long snout. Its behavior relies more on concealment and quick movements than on territoriality. In an aquarium, a long setup with a secure cover is essential because sudden jumps are possible. The species remains uncommon in the aquarium trade and requires careful acclimation. Wild individuals may also be sensitive to repeated handling and abrupt changes in water conditions.

Geographic origin and biotope

The distribution of Potamorraphis guianensis is associated with northern South America, especially the Guianas region. It occurs in freshwater environments connected to river systems and marginal areas of watercourses. The biotope includes quiet sections, vegetated edges and areas where plants or branches provide cover. Warm, clean and well-oxygenated water is suitable for its maintenance. In an aquarium, gentle to moderate filtration and plenty of swimming length are preferable to strong, turbulent flow.

Precise location and local name

The English common name Needle Fish is the name most often associated with Potamorraphis guianensis in the aquarium trade. A specific local name used by a particular community or river is not retained here. In records, the species is generally associated with the fresh waters of the Guianas and neighboring northern Amazonian basins. Because needlefish can be confused with closely related species, identification should take provenance and morphology into account. Wild specimens should be handled gently, especially during transport and acclimation.

Appearance and physical characteristics

The most striking feature of Potamorraphis guianensis is its very slender body, combined with an elongated snout that creates the characteristic needlefish profile. The fins are positioned toward the rear of the body, supporting rapid swimming and sudden acceleration. Its coloration is generally subdued, with silvery, gray or brownish tones that provide effective camouflage. The elongated mouth contains fine teeth suited to capturing small prey. A tightly fitted aquarium cover is essential because this body shape makes the fish prone to jumping when startled.

General diet

Potamorraphis guianensis is a predator of small prey and feeds mainly in the water column, often close to the surface. Its natural diet includes small fish and appropriately sized aquatic invertebrates. In aquaria, newly imported specimens usually accept live or frozen foods more readily, including small whole prey suitable for their mouth. A gradual transition toward prepared carnivorous foods may be attempted, without forcing the fish to eat. Small, frequent meals are preferable, and leftovers should be removed promptly. Small meaty foods and excellent water quality are especially important.

Essential data

• River of origin:
• Local name used: Needle Fish
• Origin of the scientific name: The genus name is associated with an elongated form and a needle-like snout.
• Full-name etymology: Potamorrhaphis comes from the Greek potamos, river, and rhaphis, needle; guianensis means originating from Guiana.
• Common/vernacular names: Needle Fish, freshwater needlefish
• Family: Belonidae
• Subfamily: Beloninae
• Name pronunciation: poh-tam-oh-RAF-iss - gwee-ah-NEN-sis
• Discovery:
• Maximum adult size (cm):
• Water temperature and pH: Stable tropical water; precise parameters not indicated.
• Appearance of the watercourse and surrounding vegetation: Quiet margins, riparian vegetation and areas providing cover.
• Typical tankmates: Small characins, open-water fishes, peaceful cichlids and small catfish.
• Temperament and behavior: Secretive, fast-moving and mainly pelagic; jumping may occur when stressed.
• Water depth: Surface and upper water column.
• Sexual dimorphism:
• Bottom structure and flow: Varied natural substrate with quiet areas and moderate current.

In your aquarium

Success with Potamorraphis guianensis depends on a long aquarium with a fully secured cover and an arrangement that reduces stress. Warm, stable and well-oxygenated water, together with sheltered areas, supports acclimation. Small meaty foods should be offered, and feeding response should be monitored closely in wild specimens. Avoid aggressive tankmates, excessively strong currents and unnecessary handling. Because availability remains intermediate, each specimen deserves patient acclimation and consistent conditions. Daily observation helps identify food refusal or signs of stress at an early stage.