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Care guide · Freshwater · fish

Marbled hatchetfish

Carnegiella strigata

Marbled hatchetfish (Carnegiella strigata)
The deep chest and dark marbling are clearly visible. Photo: Cwsbln · Source · CC BY-SA 3.0Resized and compressed; no cropping or colour changes.

The marbled hatchetfish (Carnegiella strigata) lives almost against the water surface. Its deep silver belly, dark marbling and broad pectoral fins make it unmistakable once you know what to look for. This small South American shoaling fish is peaceful, but its aquarium needs differ from those of fish that spend their time among submerged plants. A long, quiet surface zone, shelter and a carefully closed lid are essential. Food must actually reach the fish near the top. Keep at least ten and choose companions that do not create constant disturbance. A small body does not make a small, tall aquarium an adequate home. This guide focuses on surface design, real food intake and responsible community choices. Its water recommendations use a conservative care band within differing published advice, rather than attempting to reproduce environmental extremes.

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At a glance

Temperature
24–28 °C
pH
5.0–7.0
GH
5–10 °dGH
Aquarium length
At least 80 cm
Adult size
Approximately 3.5 cm
Group size
At least 10 individuals
Temperament
Peaceful

About this species

Carnegiella strigata belongs to Gasteropelecidae. The deep chest forms its characteristic hatchet outline, beneath a small upward-facing mouth and well-developed pectoral fins. Silver flanks carry dark diagonal lines and patches. Do not confuse it with a larger, mainly silver hatchetfish or another Carnegiella sold under a general trade name. Identification should involve the whole animal, not just one stripe in a blurred photograph.

The quoted adult size is approximately 3.5 cm standard length, measured without the caudal fin. Geographic variation exists, so a different pattern does not automatically establish a separate species or a documented collection locality. Well-conditioned females may look fuller, but body fullness alone is not certain sex identification. This guide does not assign an inadequately supported fixed lifespan. When buying fish, look for intact mouths, normal breathing and demonstrated feeding rather than relying on a shop label alone.

Natural habitat

The species is recorded from the Amazon region, including Colombian waters. Distribution accounts differ, so a shop group should not be assigned to a precise river biotope without provenance. Sheltered forest waters, overhanging vegetation and structures just below the surface fit its way of life. Small insects and other animal food arriving on or near the water surface can be reached there.

Translate this into quiet upper water with a mixture of shade and open space. Neither a completely dark, overgrown surface nor a bare brightly illuminated lane is the objective. Roots and bank-like planting provide cover, but should not divide the group into inaccessible pockets. Brown water is not proof of good water quality. Ask about the fish’s origin and present husbandry so acclimatisation can follow their actual circumstances rather than an imagined wild-water recipe. The aquarium can meet their needs without pretending to recreate a verified collection site.

Aquarium and layout

For a group of at least ten, use an aquarium at least 80 cm long. Usable surface area matters especially; a tall, narrow tank cannot replace horizontal swimming room. Sources also mention a 75 by 30 cm footprint. Here the more generous length guideline is used without converting it into an unsupported minimum volume. A community aquarium must additionally accommodate the other inhabitants’ groups, swimming areas and territories.

Close the aquarium carefully, including openings around cables and hoses. Startled fish can launch themselves strongly out of the water. This does not justify describing them as actively flying fish. Work calmly during maintenance and do not leave an opening unattended. Combine floating plants with open feeding spaces and gentle surface movement. Do not aim a strong filter jet through their preferred station. Filtration and gas exchange remain important: a quiet surface must not become a sealed, poorly oxygenated layer beneath excessive plant cover.

Water conditions

A practical care band is 24–28 °C, pH 5–7 and GH 5–10 °dH. Specialist sources publish broader and different ranges. The band used here is a conservative shared starting point, not proof that every combination within it suits every individual equally well. Set the actual conditions according to provenance, acclimatisation and the requirements of all inhabitants. Avoid sudden changes rather than chasing a particular number.

Add the group only to a biologically mature aquarium. Ammonia and nitrite should not be detectable. Make regular changes with appropriately prepared water and check that temperature and composition are sufficiently similar. Do not force pH rapidly with isolated additives: buffering and source water help determine what can remain stable. An exact KH target is not established here. At warmer temperatures, pay particular attention to gas exchange and normal breathing. A clean-looking tank still needs testing when behaviour or feeding changes unexpectedly.

Behaviour and group size

This is a peaceful, rather easily startled upper-water group fish. At least ten provides a better starting point than two or three individuals constantly hiding. That number is not an automatic stocking formula. Observe whether every fish can move with the group and feed, and whether a dominant companion repeatedly disrupts the surface zone. Repeated jumping, diving for cover or missing food warrants investigation of lighting, disturbance, layout and neighbours.

Small calm fish may work when temperature, hardness and layout also match. With dwarf cichlids, bottom breeding territories still matter; different swimming levels do not make a combination automatically safe. Large predators, fin-nippers and frantic food competitors are poor companions. Do not promise safety for newly hatched shrimp or fish larvae either: tiny animal prey fits this fish’s diet. Plants mainly provide cover, but leave open space along the front. Assess the finished community rather than adding species solely because a water-value chart overlaps.

Feeding

The upward-facing mouth and surface preference dictate how food should be offered. Small insects and crustaceans suit the natural animal-based diet. Alternate suitable small live or frozen prey with a complete dry food if the group genuinely accepts it. Crumble flakes where needed. Food that reaches the bottom before the hatchetfish respond has not provided a successful meal for them, however suitable its ingredient list might appear.

Distribute modest portions across open spaces between floating plants and watch who eats. A fast tetra may intercept everything while the hatchetfish merely appear calm. Dried Daphnia is supplementary food, not a complete diet and not a replacement for all other animal foods. Remove uneaten remains. With newly acquired fish, observed ingestion matters more than a full feeding ring: ask what they previously ate and change gradually. There is no universal dose independent of body size, group size and actual intake.

Breeding

Breeding information is limited and inconsistent. Some care profiles call reproduction unrecorded, whereas FishBase and the United States fish and wildlife agency’s institutional summary cite an older description of eggs falling among plants or onto the bottom. Hatching after approximately 36 hours at 25 °C is reported there. This is an observation under particular circumstances, not a guaranteed timetable for every aquarium group.

A serious attempt needs a quiet separate setup, fine spawning material and preparation for extremely small fry, rather than a recipe consisting only of lowering pH. Do not rely on parental care or safe development among adult tankmates. Arrange suitable first foods and gentle, fry-safe filtration beforehand. Use actual observations of eggs, development and ingestion to guide adjustments. The guide does not promise easy breeding or supply an unproven universal trigger or yield. Record provenance and conditions if attempting reproduction so results remain useful and distinguishable from general trade anecdotes.

Sources & review

This care guide draws on several specialist sources and was last checked on .

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