Freshwater Hatchetfish: Species and Breeding

The enlarged pectoral fins and powerful muscles enable hatchetfish to perform one of the most captivating behaviors in the aquarium hobby: aquaplaning. Rather than true flight, these fish leap out of the water and strike their pectoral fins rapidly against the water surface in a powerful downward motion. This action allows the fish to skim across the surface-with only the tail and anal fin submerged-gliding for up to 2 meters or more in the wild when escaping predators or other disturbances.

The lateral line (the sensory organ running along the fish's side) plays a critical role during these aerial escapes. In many hatchetfish species, the base of the anal fin is marked by a dark line that aligns with the water surface while the fish aquaplanes. The posterior section of the lateral line remains immersed, continuing to function and relay sensory information about pressure and balance, helping the fish correct its posture and avoid toppling.

Major Hatchetfish Species: What You'll Find in Aquariums

Hatchetfish are found across Central and South America-from Panama to Argentina-giving them widely varying natural temperature preferences depending on origin. Always ask your dealer about the source of imported fish, as Argentinian species are adapted to cooler water than Amazon basin species. There are three main genera kept by aquarists: Gasteropelecus, Carnegiella, and Thoracocharax. All share the same basic keeled shape and jumping behavior, though they vary in size, color patterns, and whether they retain an adipose fin.

Gasteropelecus Species

Common Hatchetfish (Gasteropelecus sternicla)

The Common Hatchetfish is a workhorse of the hobby, growing to about 6 cm. Native to the Amazon basin and its larger tributaries, as well as Guyana and Surinam, it displays a yellowish to yellow-green coloration with silver-reflecting scales, darker on the back and paler below. A distinctive brown-to-black lateral stripe with pale green lines above and below runs along the flank, bordered by two additional fainter lines. The dorsal fin has a dark edge; all other fins are clear.

This species is a dedicated surface feeder with a particular appetite for mosquito larvae, though it can be trained to accept quality dry foods. Notably, all hatchetfish sold today are wild-caught specimens (no commercial breeding exists), and they typically arrive above 4 cm in length. In the wild, they live in shoals, and for breeding attempts in the aquarium, you'll need at least six individuals. Newly acquired hatchets are often nervous and may refuse food; a quiet environment with calm tank mates helps them settle quickly.

Silver Hatchetfish (Gasteropelecus levis)

The Silver Hatchetfish comes from the lower Amazon and reaches 6 cm. It lacks an adipose fin and closely resembles the Common Hatchetfish, though it often displays a dark blotch at the dorsal fin base and occasionally a black streak at the anal fin base. Behavior and care requirements are virtually identical to the Common Hatchetfish, making it an equally hardy and rewarding choice for established aquariums.

Gasteropelecus coronatus

This 6 cm species from the Peruvian Amazon rarely appears in the aquarium trade. Many authorities, including fishbase.org, suggest it may be a local variant or synonym of Silver Hatchetfish, distinguished only by minor differences in tooth and fin ray counts.

Spotted Hatchetfish (Gasteropelecus maculatus)

At 9 cm, the Spotted Hatchetfish is the largest Gasteropelecus species and remains rare in the hobby despite being first introduced to Europe in 1910. Found in eastern Panama, Surinam, Venezuela, and Colombia, it displays a gray-green to brownish-green ground color with a bluish sheen in some specimens. A dark stripe runs from the gill cover to the tail, bordered above by a silver line. Individual scales are darkly pigmented, giving the fish a spotted appearance, and the dorsal fin has a dark edge.

Carnegiella Species

Black-Winged Hatchetfish (Carnegiella marthae)

The Black-Winged Hatchetfish is the smallest aquarium hatchetfish, reaching just 3.5 cm in adulthood. Native to the Venezuela, Rio Negro, and Rio Orinoco basins, it's named for the dark coloration on the middle of its pectoral fins. A dark stripe runs from the gills to the tail, bordered above by a silvery band. The breast and keel are edged in black, with fine spots along the flanks and two black bars on the cheeks. It lacks an adipose fin and was not introduced to European aquariums until 1935.

Marbled Hatchetfish (Carnegiella strigata)

The Marbled Hatchetfish was probably the most popular hatchet species in the 1950s, though it's now rarely imported. Growing to 4.5 cm, it's native to the Amazon around Iquitos and Guyana. Its yellow-green ground color shows silver by reflected light, with a dark olive back marked by darker spots and stripes. A characteristic dark stripe runs from the gill cover to the tail with a silver margin on the upper side, and three irregularly shaped black bars mark the keel. Fins are colorless and the adipose is absent. Once established, these hatchets are hardy and eager eaters. The species was first introduced to Europe in 1912, and some authorities recognize two subspecies: C. strigata strigata and C. strigata vesca.

Pygmy Hatchetfish (Carnegiella myersi)

At just 2.5 cm, the Pygmy Hatchetfish is the smallest of all aquarium hatchets, making it a unique choice for smaller setups. It comes from the Rio Ucayali in Bolivia and the Peruvian Amazon, arriving in Europe in 1957, though it is now rarely imported.

Thoracocharax Species

Giant Hatchetfish (Thoracocharax securis)

The Giant Hatchetfish grows to 9 cm and hails from fast-flowing rivers across South America, though it's rarely encountered by hobbyists despite being introduced to Europe in 1910. Its ground color is yellow-brown to pale olive with silver by reflected light. A broad line runs from the gill covers to the tail, showing blue or green highlights when light hits it. As the fish ages, its body deepens until depth and length are nearly equal. The pectoral fins are proportionally the longest of all hatchetfish species, stretching back well below the anal fin.

Spotfin Hatchetfish (Thoracocharax stellatus)

The Spotfin Hatchetfish ranges from central Brazil to Argentina and resembles the Giant Hatchetfish but with notably shorter pectoral fins. It features a black stripe on the leading edge of the dorsal fin and a less-pronounced keel than its larger relative.

Housing and Care: Essential Requirements

Hatchetfish need a secure, well-fitted aquarium cover-this is non-negotiable. Their habit of leaping, especially when startled, means they will escape and potentially perish if given the opportunity. In uncovered tanks in shops, they have been observed jumping from one tank to another, appearing in aquariums far removed from their original placement.

Water Parameters and Temperature

Surprisingly, for fish primarily from the Amazon, hatchetfish are not particularly sensitive to water hardness. They adapt well to a range of conditions, whether London tap water or other regional sources. For general care, neutral to slightly acidic water suits most species. Confirm the geographic origin of your specimens with your dealer, as Argentinian populations are acclimated to cooler temperatures than Amazon basin species.

Tank Mates and Behavior

Hatchetfish are peaceful but should never be kept singly or in pairs-they live in shoals in the wild and are far more confident and hardy in groups of at least six. They do not compete well for food at lower levels and will not pick food from the bottom of the tank. Be mindful that they will eat small fry or other organisms that fit in their mouths, including the fry of your best livebearers, so tank mate selection should reflect their peaceful but opportunistic feeding habits.

Feeding

In the wild, hatchetfish are surface feeders with a particular fondness for mosquito larvae. In the aquarium, most species can be encouraged to accept quality dry foods, though some remain somewhat selective. Because they rarely venture to lower tank levels, uneaten food can accumulate on the gravel, fouling water quality. Regular siphoning or the addition of a bottom-feeding catfish species helps manage debris.

Breeding Hatchetfish in Captivity

Breeding success with hatchetfish is uncommon but achievable. Silver Hatchetfish is the most documented success story, though other species have been bred in aquariums. Here's what successful breeders have learned:

Silver Hatchetfish Breeding Behavior

In successful captive spawns, the male drives the female (not by aggressive chasing, but by swimming alongside her) into fine-leaved plants. The pair deposits eggs among these plants in a behavior that mirrors wild spawning, which occurs among the fine roots of plants along river banks in South America.

Although single pairs have spawned in captivity, communal spawning is likely the norm in the wild, suggesting that group spawning dynamics play a role in reproductive success. Eggs hatch in approximately 30 hours, and fry care mirrors that of common tetras-they require infusoria and fine live foods initially before transitioning to crushed dry food and small particles.

Conditions Favoring Breeding

• Group size: At least six individuals, preferably more to mimic wild shoaling behavior
• Water softness: Softer water is preferable for breeding, even if established fish tolerate harder water
• Quiet environment: Minimize disturbances and stress
• Fine-leaved plants: Provide dense plantings for spawning substrate and fry shelter
• Stable conditions: Avoid sudden changes in temperature or water chemistry

Important Caveat

No commercial hatchetfish breeding exists; all specimens sold in aquariums are wild-caught. This reflects both the complexity of captive breeding and the ongoing availability of wild populations. If you undertake a breeding project, you're participating in a rare and valuable contribution to the hobby's knowledge base.

Key Takeaways for Hatchetfish Keepers

Hatchetfish are visually striking and behaviorally fascinating additions to any aquarium, offering the unique spectacle of aquaplaning behavior that few other fish can replicate. They settle well in quiet environments, tolerate a range of water conditions, and are generally hardy once established. Always cover their tank securely, keep them in groups, manage uneaten food carefully, and confirm the geographic origin of your specimens to match their temperature preferences. If you're interested in the challenge of captive breeding, Silver Hatchetfish offer the best documented path to success.