The Marbled Hatchetfish is a unique surface dweller capable of true flight. A peaceful schooling species requiring a tight-fitting aquarium lid.
Overview
The Marbled Hatchetfish (Carnegiella strigata) is one of the most unusual freshwater fish available to aquarists. This species belongs to the family Gasteropelecidae and inhabits the Amazon River basin, primarily in flooded forests and slow-moving tributaries across Peru, Colombia, and Brazil. Its natural habitat consists of dark waters beneath the tropical forest canopy, where these fish stay near the very surface.
The most remarkable feature of the Marbled Hatchetfish is its genuine ability to fly. Unlike most "flying" fish that merely leap from the water, Carnegiella strigata possesses powerful pectoral muscles attached to a keel-shaped extension of the sternum. This allows the fish to actively beat its pectoral fins and glide above the water surface for distances of several meters. In the wild, this mechanism serves as an escape response from predators.
The body is laterally compressed with a distinctive hatchet shape — deep-bodied with a pronounced keel along the lower profile. The coloration is silvery with an intricate marbled pattern of dark brown and black lines radiating from the back toward the belly. Adults reach 3–4 cm in length, making them one of the smallest members of the family.
Tank Requirements
The minimum aquarium volume for a group of Marbled Hatchetfish is 60 liters. The single most important requirement is a tight-fitting lid with no gaps whatsoever. This is not a suggestion but an absolute necessity: these fish can and will jump through the smallest openings and perish on the floor. In practice, you should seal even the holes for cables and tubing.
Optimal water parameters:
- Temperature: 24–28 °C
- pH: 6.0–7.0
- General Hardness (GH): 2–15
Marbled Hatchetfish prefer subdued lighting. Floating plants are essential — water lettuce, salvinia, or riccia work well. They diffuse the light, create a sense of overhead cover, and reduce stress. Water flow should be gentle, as these fish naturally inhabit still and slow-moving waters. Driftwood and leaf litter make excellent decorations, tinting the water and bringing conditions closer to their natural environment.
Feeding and Diet
Carnegiella strigata is a surface-feeding insectivore. In nature, these fish feed on small insects that land on the water surface and their larvae. In the aquarium, it is important to understand that hatchetfish feed exclusively at the surface — anything that sinks below is typically ignored.
The diet should consist of:
- High-quality flakes or floating micro-pellets
- Frozen bloodworms, brine shrimp, and daphnia
- Live fruit flies — the best treat, closely replicating their natural food source
- Cyclops and small brine shrimp for juveniles
Feed 1–2 times daily in small portions. Food should remain on the surface and be consumed within 2–3 minutes. If you keep hatchetfish alongside bottom dwellers such as Kuhli Loach, there is typically no competition for food since the species feed at different levels.
Care and Maintenance
The Marbled Hatchetfish is a relatively undemanding species provided that water parameters remain stable. Weekly water changes of 20–25% help maintain water quality. Filtration should be effective but without strong current — an internal filter with adjustable flow or a sponge filter works well.
Monitoring parameter stability is crucial: Marbled Hatchetfish are sensitive to sudden fluctuations in pH and temperature. When performing water changes, use water that has been prepared to match the existing parameters. Regularly test ammonia and nitrite levels — both should read zero.
These fish are susceptible to ich and velvet disease, particularly when stressed from shipping or sudden changes in conditions. A quarantine period of 2–3 weeks after purchase is recommended. Watch their behavior closely: healthy hatchetfish actively school near the surface, while retreating to hiding spots or motionless hovering may indicate problems.
Compatibility
Marbled Hatchetfish are exceptionally peaceful schooling fish. They must be kept in groups of at least 6 individuals, ideally 8–10. In smaller groups, the fish become skittish and experience chronic stress, which weakens the immune system and shortens their lifespan.
Because hatchetfish occupy exclusively the upper water layer, they coexist beautifully with virtually any peaceful species that inhabit the middle and lower zones. Excellent tank mates include:
- Small tetras: Ember Tetra, Black Neon Tetra, Black Phantom Tetra
- Rasboras: Harlequin Rasbora, Hengel's Rasbora
- Bottom dwellers: Kuhli Loach, Otocinclus
- Dwarf cichlids: Nannacara
Avoid keeping Marbled Hatchetfish with large or aggressive fish, as well as active species that create strong currents or compete for surface space. Stay away from large cichlids, barbs, and active predators.
Breeding
Breeding Carnegiella strigata in the home aquarium is a challenging endeavor that rarely succeeds even for experienced aquarists. These fish are egg scatterers that deposit eggs among plant roots.
To stimulate spawning, conditions approximating the onset of the rainy season must be recreated:
- Gradually lower the water level, then simulate "rains" by adding soft, cool water
- Reduce hardness to a minimum (GH 2–4, KH below 1)
- Maintain a slightly acidic environment (pH 5.5–6.5)
- Raise the temperature slightly to 27–28 °C
- Feed generously with live foods (fruit flies, small brine shrimp) for 1–2 weeks
The female scatters fine eggs among the roots of floating plants, predominantly in the evening hours. After spawning, the parents must be removed as they are prone to eating their own eggs. Incubation lasts 24–36 hours. The larvae are extremely small and subsist on their yolk sacs for the first few days. First food should be infusoria and micro-worms, transitioning to baby brine shrimp after 7–10 days.
The primary difficulty in breeding lies in the very small number of eggs produced (typically 3–10 per spawning event) and the high sensitivity of fry to water quality. Successful rearing requires clean, stable conditions and regular feeding in small portions 3–4 times daily.