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FishmediumFreshwater

Spotted Hatchetfish

Gasteropelecus maculatus

Also known as Giant Hatchetfish

Gasteropelecidae

📍 South America; Colombia, Panama, and northwestern Venezuela, primarily in slow-moving or still blackwater streams, forest pools, and tributaries of the Atrato and Magdalena river systems

The Spotted Hatchetfish is a small, surface-dwelling fish with a distinctively deep, keel-shaped chest and a flattened back, silver body adorned with irregular dark spots along the flanks and a horizontal dark stripe. It is a peaceful schooling species that occupies the very top of the water column and serves as an active, visually interesting upper-level inhabitant in community aquaria.

Size1.5"
Min Tank20g
School6+
peaceful
Zonetop

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Care Guide

Diet

In the wild, Spotted Hatchetfish are surface insectivores that feed on small insects, larvae, and invertebrates that fall onto or rest at the water surface. In captivity they accept high-quality floating flake foods, micro pellets, and relish live or frozen foods such as fruit flies, small crickets, bloodworms, and daphnia. Feeding at the surface is essential, as they rarely venture lower in the water column to retrieve sinking food.

Behavior

Spotted Hatchetfish are highly social and must be kept in groups of at least six individuals to feel secure and display natural behavior; solitary or small groups become stressed and reclusive. They are exclusively surface dwellers and possess enlarged pectoral muscles that allow them to leap from the water, making a tight-fitting lid an absolute necessity. They are completely non-aggressive toward tankmates and coexist peacefully with other small, gentle species occupying lower water zones.

Breeding

Breeding Spotted Hatchetfish in captivity is rarely achieved and considered difficult; conditioning pairs with abundant live foods and replicating soft, acidic blackwater conditions with dim lighting and floating plants may encourage spawning. Eggs are reportedly scattered among fine-leaved floating plants near the surface, and parents do not provide care and may consume eggs if not separated. Fry are extremely small and require infusoria or commercial fry foods initially, making successful rearing a significant challenge.

Common Diseases

Ich (White Spot Disease)

Symptoms

Fine white spots resembling grains of salt on the body and fins, flashing against surfaces, lethargy, and loss of appetite.

Treatment

Gradually raise water temperature to 28-30 C to accelerate the parasite's life cycle, and treat with a copper-based or formalin medication; hatchetfish are sensitive to medications so use half doses and monitor closely.

Velvet (Oodinium)

Symptoms

Gold or rust-colored dust-like coating on the skin, rapid gill movement, clamped fins, and rubbing against objects.

Treatment

Dim the tank lighting (the parasite is photosynthetic), treat with a copper-based medication at reduced dose, and perform partial water changes; quarantine affected fish promptly.

Bacterial Fin Rot

Symptoms

Fraying, disintegrating, or discolored fin edges, sometimes with a white or red border at the margin of deteriorating tissue.

Treatment

Improve water quality immediately with partial water changes, identify and remove stressors, and treat with a broad-spectrum antibacterial medication such as kanamycin or nitrofurazone at the recommended dose.

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Quick Facts

diet
Insects, small invertebrates, high-quality flake and frozen foods
lifespan
3-5 years
max size
3.5 cm (1.5 in)
tank size
20 gallons minimum

Water it likes

ph
5.5-7.0
ammonia
0 ppm
nitrate
<20 ppm
hardness
1-10 dGH
temperature
73–82°F (23–28°C)

Legality

No state or federal restrictions on record for this species.

Not legal advice, and possibly incomplete or out of date. Rules vary by state and locality and change over time — always confirm the current regulations with your state wildlife or agriculture agency before buying, keeping, or shipping this species.

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Kept by0 hobbyists