Freshwater Hatchetfish (Gasteropelecidae)

Hatchetfish

Gasteropelecus sternicla

The scientific name Gasteropelecus sternicla refers to hatchetfish, belonging to the family Gasteropelecidae. These fish are notable for their unusual appearance. Their original body shape is not the only distinguishing feature; their feeding method, where the fish leap out of the water, spreading their pectoral fins to maneuver in flight to catch insects, is also of interest.

Tank
from 108 L (29 gal), 110 L (29 gal) recommended
Temperature
22 – 28 °C (72 – 82 °F)
Size in aquarium
6 cm (2.4 in)
Acidity
pH 6–7
Natural rangeRange on the map
  • South America area
  • Brazil
  • French Guiana
  • Guyana
  • Peru
  • Suriname
  • Venezuela

Tank conditions

Plan the tank stocking
Temperature
22 – 28 °C (72 – 82 °F)
Water pH
Slightly acidic (6) – Neutral (7)
Water dH
Very soft (2) – Hard (15)
Water salinity
no salt (freshwater)
Size in aquarium
6 cm (2.4 in)
Lifespan
5 years
Temperament
Peaceful (regular)
Toward small fish
not a predator
Required aquarium volume
from 108 L (29 gal), 110 L (29 gal) recommended
Lighting
moderate (regular)
Substrate
any (no restrictions)
Water flow
weak or moderate
Swimming level
near the surface
Feeding
Meat / protein live, frozen, fresh
Keeping
Medium group 6–8 individuals
Jumping
high a tight-fitting lid is essential
  • Lifespan. A lifespan to expect under good care, not a measured value: it depends heavily on tank volume, water quality and diet — and for selectively bred forms, on their origin as well.
  • Toward small fish. Based on the Predators category in the catalog or the temperament in the species parameters. “A risk to small fish” means the species is not a predator by habit, yet will swallow any fish that fits in its mouth.
  • Required aquarium volume. The 108 L minimum corresponds to a tank footprint of 120×30 см. The recommended 110 L is for the group size given under keeping mode.

Care and keeping

Description

A distinctive feature of this fish is its body: flattened on the sides, with a pronounced belly, it truly resembles an axe blade. The mouth is positioned quite high on the head, which facilitates gathering food from the water surface. The long and rigid pectoral fins spread out like wings during a jump, providing the fish with the necessary maneuverability. The main body coloration is silvery, complemented by dark speckles and a stripe that runs along the entire body from head to tail.

Habitat

These amazing fish were first described in South America as early as 1758, in the mid-18th century. Hatchetfish inhabit vast territories of the Amazon River basin, preferring small rivers and streams rich in floating vegetation. They usually stay in the upper layers of the water, but instantly dart into the depths when danger arises. In their natural environment, their primary diet consists of insects.

Behavior and Compatibility

This species is distinguished by its peaceful and even somewhat shy nature, so keeping them with aggressive tankmates is completely unacceptable. It is recommended to form groups of at least 6 individuals. They get along perfectly with other small, calm, and unhurried fish.

Care and Maintenance

Hatchetfish have high demands for water purity and are extremely sensitive to any fluctuations in pH and dGH parameters, which can significantly reduce their immunity. A standard set of aquarium equipment is mandatory: aeration, heating, lighting system, and filtration. It is advisable to use a filter with an element that acidifies the water. It is important to remember that the aquarium must be reliably covered with a lid, as these fish are prone to jumping. In aquarium decoration, preference should be given to floating plants, such as water lilies, whose leaves on the surface provide shelter for the fish. Other decorative elements do not play a significant role.

Diet

In their natural habitat, these fish are exclusively predators, feeding on larvae and adult insects collected from the water surface. In aquarium conditions, they easily adapt to dry commercial foods floating on the surface. Freeze-dried insect-based products, such as bloodworms or daphnia, would be an optimal choice. In summer, the diet can be enriched with live foods: mosquito larvae, bloodworms, small fruit flies, and common flies.

Breeding and Reproduction

Cases of successful breeding of these fish in home aquariums are extremely rare. This is mainly done by professional breeders working for commercial purposes, who then supply the offspring to retail trade networks.

Diseases

Hatchetfish are often susceptible to Ichthyobodo disease. The main cause of its occurrence is unsatisfactory water quality. This disease is especially common in newly acquired fish. If the aquarium has a mature biological environment and all water parameters are maintained within normal limits, health problems generally do not arise.

How to choose

When purchasing, choose active individuals that stay in a school and exhibit natural behavior. Avoid fish with damaged fins, signs of emaciation, white film, or spots on the body, as this species is sensitive to stress during transport and prone to infectious diseases. In the store, the fish should stay near the water surface, which is characteristic of their species. Before purchasing, make sure there are no signs of Ichthyobodo or other parasites in the aquarium with the fish, as newly bought individuals often require quarantine to adapt to new conditions.

Compatibility

There are no pair reviews for this species yet — check tankmates in the matcher.

All tankmates

Plants and this fish

Matching water does not mean the plant will stay intact.

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does Hatchetfish get?

An adult reaches 6 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Hatchetfish need?

The recommended volume is 110 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Hatchetfish need?

Temperature 22–28 °C, pH 6–7, hardness 2–15 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Hatchetfish live?

Around 5 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Hatchetfish aggressive?

Temperament: peaceful (regular). Keep this in mind when choosing tank mates.

How many Hatchetfish should be kept together?

Recommended setup: medium group (6–8 individuals). Ignoring this is a common cause of stress and disease.

What does Hatchetfish eat?

Diet type: meat / protein (live, frozen, fresh). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Hatchetfish?

The scientific name of the species is Gasteropelecus sternicla, family Freshwater Hatchetfish (Gasteropelecidae). It also appears in the literature as: Clupea sternicla, Gasteropelecus argenteus, Gasteropelecus coronatus.

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Other scientific names and conservation status

Other scientific names
Clupea sternicla, Gasteropelecus argenteus, Gasteropelecus coronatus, Salmo gasteropelecus
Categories
Characins
Conservation status
Least concernLC