Dusky Narrow Hatchet Fish (Triportheus angulatus)

Common Name

Dusky Narrow Hatchet Fish
Triportheus angulatus

A large river hatchetfish with a glider chest and long pectorals that looks built for takeoff. It is rarely seen in the hobby compared to the small marbled hatchetfish found in shops, partly because it grows larger, needs a long tank, and is an expert jumper. When it appears, it turns the surface into a runway and becomes a true conversation piece.

Origin and Habitat

Native to tropical South America across much of the Amazon basin, including main channels, floodplain lakes, and seasonally flooded forests. It schools near the surface over sand and fine sediment, then follows the annual flood pulse into the trees where it feeds beneath overhanging vegetation. Water clarity ranges from clear to tea-stained. Flow is gentle to moderate along protected margins, and submerged wood and tall shoreline plants create foraging lanes just under the surface.

Temperature and Water Conditions

Target 24 to 28 °C (75 to 82 °F), with very clean water and high dissolved oxygen. Wild reports show a broad pH envelope from about 5.0 to 8.0 depending on location and season, often slightly acidic to neutral in floodplain habitats. We do not recommend chasing or altering water parameters except in special breeding situations. Stable conditions are far more important.

• Keep ammonia and nitrite at zero, nitrate low, and temperature steady.
• Use a perfectly tight lid with no gaps.
• Create vigorous surface agitation through spray bars or upward filter returns to keep oxygen saturation high.

Appearance and Size

Think hatchetfish scaled up. The chest is deep and keeled, the pectoral fins are long and scythe-like, and the body is bright silver with a gentle dusky cast that shifts with mood and light. Adults commonly reach 15 to 18 cm total length (about 6 to 7 inches), with larger scientific records around 23 to 24 cm (about 9 inches) for robust river specimens. Males are usually slimmer and a touch smaller than females.

Diet in the Wild

A floodplain omnivore that shifts with the seasons. During high water it takes fruits and seeds that drop from riverbank trees along with terrestrial insects. During lower water it feeds more on aquatic insect larvae, zooplankton, and small crustaceans. The constant theme is surface and near-surface foraging while cruising in schools.

Feeding in Captivity

Match the surface-feeding lifestyle with buoyant foods.

• Floating sticks and flakes
• Small floating pellets
• Frequent live or frozen items such as fruit flies, wingless Drosophila, mosquito larvae, daphnia, and brine shrimp
• Include a plant-based item once or twice per week (e.g., spirulina pellet or softened vegetable bits)

Feed modest portions two or three times daily so the school stays active without fouling the water.

Behavior and Tank Setup

Fast, social, and alert. Keep in a group of at least six to spread out skittish behavior. Provide a long footprint with open water lanes and soft shelter at the sides from wood and tall plants.

• Starting footprint: about 120 × 45 cm (48 × 18 in) suits juveniles and smaller groups
• Full-grown schools deserve larger quarters
• Keep flow gentle to moderate with high dissolved oxygen
• Use floating cover to reduce startle runs

Good companions include peaceful midwater tetras of size, larger pencilfish species, calm cichlids that ignore top dwellers, Corydoras, and other non-nippy bottom fish. Avoid fin nippers and very aggressive species.

Breeding

In nature this species follows the hydrological calendar, building condition during rising water and releasing pelagic or semi-pelagic eggs during or after the peak. Captive spawning is rarely reported and likely requires seasonal cues, a very large tank, gentle current, and heavy feeding with live foods.

If attempted:

• Simulate a wet season with frequent small water changes and slightly warmer rain temperature
• Provide open swimming space with floating plants
• Use an egg saver such as marbles or a mesh grate so eggs fall out of reach
• Remove adults after spawning
• Rear eggs in very clean, well-aerated water
• Start fry on infusoria or a micro diet, then rotifers and newly hatched brine shrimp

Breeder’s Tips

• Triggers: increase live foods, add daily small water changes that slightly raise water level, and soften light with floating plants
• Egg protection: cover the base with marbles or a plastic grate so eggs fall through; a shallow layer of larger rounded gravel also helps hide eggs
• First foods: begin with infusoria or a commercial micro diet, then offer rotifers and newly hatched brine shrimp
• Water change rhythm: change 5–10 % daily with closely matched temperature and chemistry
• Group management: condition a large school, then move a well-conditioned subset to the spawning tank to improve egg survival

Quick Facts

• Scientific name: Triportheus angulatus
• Common name: Dusky Narrow Hatchet Fish
• Origin: Amazon basin floodplains and channels in tropical South America
• Adult size: commonly 15–18 cm TL (6–7 in), large records near 23–24 cm (9 in)
• Temperature: 24–28 °C (75–82 °F)
• pH: 5.0–8.0 recorded in nature, keep stable rather than exact
• Hardness: soft to moderate, clean and well oxygenated
• Temperament: active schooling surface dweller, nervous if kept in small numbers
• Diet: surface omnivore that shifts seasonally between fruits/seeds, insects, zooplankton, and small crustaceans
• Breeding: flood-pulse broadcast spawner; use marbles or a grate to protect eggs if attempted

Tropical Fish Co. Notes

A true oddball that gives a big river vibe at the very top of the water column. Because it is larger than the usual hatchetfish and launches like a missile, it remains rare in the hobby and appears only occasionally. Give it length, a perfectly tight lid, high dissolved oxygen from vigorous surface agitation and reliable filtration, and calm neighbors. In a planted display with floating cover you get constant surface motion and a school that gleams like chrome when it turns in the light