Spotted hatchetfish
Gasteropelecus maculatus
A fish with a unique shape — the laterally compressed body and expanded ventral profile resemble a hatchet blade. Exclusive surface swimmer, it is one of the few freshwater fish capable of true gliding flight above the water thanks to powerful pectoral muscles. Native to Central and South American rivers. Airtight lid is not optional: jumps are legendary and a gap of a few centimeters is enough for escape. In schools of 6–8+ in the upper zone with floating plants and dim lighting, it creates a unique scenic effect. Surface insectivore: prioritize floating food and fruit flies.
Water Temperature
24 - 28 °C
pH Value
6 - 7
Water type
Freshwater
Tank level
Surface
Adult size
6.4 cm
Minimum tank volume
>= 80 L
Minimum group
>= 6
GH
2 - 12 dGH
KH
1 - 6 dKH
TDS
40 - 240 ppm
Conductivity
63 - 375 uS/cm
Species description
Geographical Origin and Habitat: Widespread from Central America (Panama) to South America (Colombia, Venezuela). Inhabits slow lakes, quiet river oxbows and flooded forest areas with abundant floating vegetation and slightly turbid waters.
Taxonomy and Morphology: Spotted Hatchetfish (Gasteropelecidae family). Hyper-compressed body laterally and monstrously protruding ventral keel (half-moon or axe shape), which houses powerful pectoral muscles for flight. Length 6-7 cm (2.5 inches).
Social Behavior: Absolutely gregarious and peaceful; lives its entire existence flattened against the surface of the water. Terrified by sudden movements, it reacts with lightning-fast sprints jumping out of the water, "flying" flapping its pectoral fins to escape predators.
Coloration and Sexual Dimorphism: Brilliant silvery body with an opaque olive green back to blend in. The flanks are studded with characteristic rows of black and brown spots, which distinguish it from other hatchetfish. No visually evident sexual dimorphism.
Care, breeding and tankmates
Aquarium Setup: Heavy and totally airtight glass lid MANDATORY (will jump out even from the slits for the tubes). Calm tank with floating plants (Pistia, Limnobium) under which it can take shelter, while still leaving ample free swimming areas on the surface.
Diet and Feeding: Very strict surface insectivore. The mouth is turned totally upwards: it will ignore any food that sinks. Feed with fruit flies (Drosophila), high quality floating flakes and freeze-dried bloodworms/brine shrimp.
Water Quality: Requires soft and slightly acidic water (pH 6.0 - 7.0, GH 2-12). Temperature 24-28°C (75-82°F). Being confined to the surface, it is hypersensitive to the too strong currents created by the filter outlet and to bacterial biofilms on the water surface.
Compatibility and Cohabitation: Perfect for quiet Amazonian community tanks. Cohabits beautifully with peaceful Tetras (Cardinals, Rummy-nose), Corydoras, Apistogramma and Loricariids. Do not combine with voracious Cichlids or competitive surface fish (like Zebra Danios).
Aquarium Breeding: Rare and poorly documented event in the amateur field. Courtships involve long jumps out of the water and the eggs are scattered among the roots of floating plants (e.g. Water Hyacinth). The fry is extremely minute.
Risks and Diseases: Death from traumatic impacts or lethal jumps (on the floor or stuck in the lamps) is the cause of death of 95% of the specimens. Highly prone to Ich (White spot) if the aquarium is subjected to cold surface drafts when opening the lid.
Geographic Origin and Distribution
Widespread from Central America (Panama) to South America (Colombia, Venezuela). Inhabits slow lakes, quiet river oxbows and flooded forest areas with abundant floating vegetation and slightly turbid waters.
Origin
Tropical oceans and reefsExtra-Amazon South AmericaCentral America and Caribbean
Fish profile
- Temperament
- Peaceful
- They are exceptionally peaceful, shy, and somewhat easily startled fish. When kept in suitably large schools, they hover calmly at the surface, providing a beautiful and unique dynamic to the tank. Startling them can result in chaotic jumping, so sudden movements near the tank should be avoided.
- Diet
- Insectivore
- They are obligate surface feeders that strictly hunt for insects and small crustaceans at the water's line. High-quality floating flakes, micro-pellets, and freeze-dried bloodworms are ideal for their daily diet. Supplementing with live fruit flies or tiny crickets triggers their natural surface-hunting instincts.
- Life expectancy
- 3-5 years
- Under optimal care, the spotted hatchetfish has a lifespan of 3 to 5 years in captivity. To reach this age, they require stable water parameters, high-quality nutrition, and a stress-free environment. Exposure to sudden changes in temperature or poor water quality can significantly shorten their lifespan.
- Adult size
- 6.4 cm
- The catalog's scalar value is 6.4 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 6.4 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Gasteropelecus maculatus (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- School
- There are no obvious color differences between the sexes in this species. Females generally possess a rounder, thicker profile when viewed from above, especially when carrying eggs. They are highly social schooling fish and must be kept in groups of at least six to feel secure.
- Feeding frequency
- Twice daily
- Offer them small amounts of floating food once or twice a day. It is critical to ensure that the food remains on the surface long enough for them to eat, as they will rarely chase sinking food. Careful observation during feeding ensures they aren't outcompeted by fast-swimming mid-water fish.
- Bioload
- Low
- The Spotted Hatchetfish has a minimal bioload footprint, making them excellent candidates for moderately sized community tanks. Standard hang-on-back or gentle canister filtration is more than adequate to manage their waste. Routine weekly water changes are sufficient to maintain pristine water conditions.
- Flow
- Moderate
- They prefer slow to moderate water flow, mimicking the quiet, shaded rivers of Central and South America. Strong surface agitation should be avoided as it makes it difficult for them to feed effectively. A gentle current running the length of the tank encourages their natural hovering behavior.
- Jump risk
- Yes
- Hatchetfish possess the highest jump risk of almost any aquarium species due to their powerful pectoral fins designed for leaping to catch insects. A completely sealed, heavy lid with absolutely zero gaps is an absolute necessity. Even small openings around filter returns or heater cords must be tightly plugged.
- Reproduction
- Oviparous
- Captive breeding is very rare and challenging, often requiring specific environmental triggers like simulating the rainy season. They are egg scatterers that deposit their eggs among floating plant roots. If successful spawning occurs, the adults must be removed, and the microscopic fry require infusoria to survive.
- Compatibility & tankmates
- Aggressive
- They are extremely peaceful top-dwellers that ignore fish residing in the middle and lower water columns. Excellent tank mates include small tetras, Corydoras catfish, and peaceful dwarf cichlids. They should never be housed with fin-nippers or large, boisterous species that might easily stress them.
- Tank level
- Top
- They strictly inhabit the absolute top layer of the water column, hovering just beneath the water's surface. They rarely, if ever, venture into the middle or bottom zones of the aquarium. Providing dense floating plants gives them a sense of security and a natural environment to hunt beneath.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.3 ± 0.4 se
- Phylogenetic uniqueness (PD50)
- 0.627
- Bayesian Length-Weight
- a = 0.01698, b = 3.09
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
