Freshwater Hatchetfish (Gasteropelecidae)

Pygmy Hatchetfish

Carnegiella myersi

Carnegiella myersi, known as the Pygmy Hatchetfish, belongs to the Gasteropelecidae family. This miniature predator specializes in hunting small insects found near the water's surface. Distinctive features of this fish include not only its small size but also its characteristic 'hatchet-shaped' body. Despite its uniqueness, the popularity of this fish in aquaristics is limited: breeding in home aquariums is extremely difficult, which explains its rare presence in pet stores.

Tank
from 40 L (11 gal)
Temperature
23 – 26 °C (73 – 79 °F)
Size in aquarium
2.5 cm (1 in)
Acidity
pH 4–7
Natural rangeRange on the map
  • Brazil
  • Peru

Tank conditions

Plan the tank stocking
Temperature
23 – 26 °C (73 – 79 °F)
Water pH
Acidic (4) – Neutral (7)
Water dH
Very soft (2) – Soft (6)
Water salinity
no salt (freshwater)
Size in aquarium
2.5 cm (1 in)
Lifespan
4 years
Temperament
Peaceful, calm/shy/inactive
Toward small fish
not a predator
Required aquarium volume
from 40 L (11 gal)
Lighting
dimmed
Substrate
sandy (regular, light)
Water flow
none or stagnant (no flow)
Swimming level
near the surface
Feeding
For carnivores live fish, insects, etc.
Keeping
Medium group 6–8 individuals
Jumping
noticeable a lid is needed
  • 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. This is a husbandry recommendation, not a measured value: the volume depends on the keeping mode (medium group (6–8 individuals)), footprint, decor and tank mates.

Care and keeping

Description

Adults reach only 2.5 cm in length. Through their translucent body, which has an unusual shape resembling a hatchet with a rounded blade, internal organs are visible. A dark stripe runs from head to tail along the midline.

Habitat

The origin of this species is linked to South America, specifically the Amazon River basin, located in modern-day Peru. The fish prefers to inhabit shaded streams and channels of the tropical rainforest, where the aquatic environment is often rich in plant fragments such as leaves, branches, and snags.

Behavior and Compatibility

Shy by nature due to their size, but generally peaceful fish. It is advisable to keep them in groups of at least 6 individuals. Suitable tank mates include species of comparable size and temperament, as well as other hatchetfish.

Care and Maintenance

For successful keeping of these fish, an aquarium of at least 40 liters is required. When setting up the tank, special attention should be paid to the upper part of the reservoir; the rest of the arrangement can be adapted to the needs of other inhabitants, if any. Several floating plants should be placed on the water surface, grouped so that they occupy no more than half of the area. Dried leaves, soaked for several days beforehand (to prevent them from floating), can be placed on the bottom. Fallen leaves will serve as a natural source of humic substances, which will impart tannins and a slight brownish tint to the water, characteristic of natural waters in the pygmy hatchetfish's habitat. During activity, whether hunting low-flying insects or reacting to fright, the fish may accidentally jump out of the aquarium; to prevent this, it is recommended to use a lid or cover glass. The basic equipment kit includes a filtration and aeration system, a heater, and lighting fixtures. Equipment settings should match the fish's needs: low light levels and no strong currents. Recommended water parameters are characterized by an acidic pH level and low carbonate hardness.

Diet

This is an insectivorous species that feeds on small insects and their larvae, obtained from the water's surface. Optimal feeding options include live or dried fruit flies (Drosophila), as well as finely chopped parts of other insects. It is important to note that the Pygmy Hatchetfish consumes food exclusively from the water surface; objects in the water column or at the bottom do not interest it.

Breeding and Reproduction

Breeding this species in aquarium conditions is extremely difficult, and there are practically no reliable methods for obtaining offspring. In their natural habitat, the fish are egg-layers. Sexually mature females, when ready to spawn, can be identified by a rounded abdomen filled with eggs, which become visible under transmitted light.

Diseases

Balanced nutrition and properly selected keeping conditions are the best prevention of diseases in freshwater fish. If the first signs of illness appear, such as changes in coloration or behavior, the first step should be to check the water parameters and quality. If necessary, all values should be brought back to normal, and only then should treatment begin.

How to choose

When selecting fish, pay attention to the following signs: — activity of individuals and absence of visible damage to fins or scales — cleanliness and clarity of the water in the retail aquarium, indicating proper care — general condition of the school, as the fish should exhibit typical behavior near the water surface — absence of signs of emaciation or unnatural spots on the body. It is recommended to acquire a group of at least 6 individuals at once, as the species is schooling and sensitive to stress when kept alone.

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 Pygmy Hatchetfish get?

An adult reaches 2.5 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Pygmy Hatchetfish need?

The recommended volume is 40 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Pygmy Hatchetfish need?

Temperature 23–26 °C, pH 4–7, hardness 2–6 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Pygmy Hatchetfish live?

Around 4 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Pygmy Hatchetfish aggressive?

Temperament: peaceful, calm/shy/inactive. Keep this in mind when choosing tank mates.

How many Pygmy Hatchetfish should be kept together?

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

What does Pygmy Hatchetfish eat?

Diet type: for carnivores (live fish, insects, etc.). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Pygmy Hatchetfish?

The scientific name of the species is Carnegiella myersi, family Freshwater Hatchetfish (Gasteropelecidae).

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Other scientific names and conservation status

Conservation status
Least concernLC