🐟 AquaticCare difficulty: IntermediateLegal complexity: Low
Marbled hatchetfish
Carnegiella strigata · also called Marble hatchetfish, Striped hatchetfish, Marbled hatchet
A small, peaceful surface-dwelling characin with a deep, marbled, hatchet-shaped body and the genuine ability to leap and beat its pectoral fins to skim across the water; charming but a notorious escape artist that demands a tightly sealed tank.
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Quick facts
| Size | Small, reaching about 3.5-4 cm (1.4-1.6 in), with a deep, hatchet-shaped keel-like belly. |
| Lifespan | 2–5 years |
| Social needs | group |
| Native region | Northern South America (Amazon basin blackwater streams of Brazil, Peru, and the Guianas) |
| Origin | New World |
| Climate | 🌴 Tropical |
| Water type | 💧 Freshwater |
| Family | Gasteropelecidae |
| Genus | Carnegiella |
Part of the Hatchetfish
Small, deep-bodied surface-dwelling characins of the family Gasteropelecidae from Central and South America, named for their keel-like 'hatchet' bellies and their remarkable ability to leap and skim across the water. Peaceful shoaling top-dwellers, they need calm, soft water, floating cover, and above all a tightly sealed tank to prevent escapes.
More hatchetfish coming soon.
Habitat & space requirements
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
Habitat & enclosure
Marbled hatchetfish are dedicated surface dwellers from shaded Amazon blackwater streams, so they need a tank with ample surface area, calm water, and floating cover; a group does well in 75 L (20 gallons) or more, prioritizing surface footprint over depth. They prefer warm, soft, acidic water: temperature 24-28 C (75-82 F), pH 5.5-7.0, and soft hardness, ideally with tannin-stained 'blackwater' conditions. Gentle flow keeps the surface calm enough for them to feed and rest.
The single most important point is a completely sealed, gap-free lid: these fish are powerful jumpers that genuinely glide across the water and will hurl themselves out of any opening. Floating plants give them security and shade and reduce jumping by making them feel covered, while subdued lighting suits their shy nature. Stable, mature, well-oxygenated water is essential as they dislike sudden changes.
Substrate
Substrate is secondary for these surface fish; a dark fine sand or gravel base with leaf litter and driftwood supports a natural blackwater look. The real focus is the upper water column, so dedicate attention to floating plants and surface cover rather than the tank floor.
Equipment & setup
Use gentle filtration that keeps the surface calm, such as a sponge filter or baffled outflow, with a heater for warm temperatures. A completely sealed, gap-free lid is the most important piece of equipment; subdued lighting and floating plants reduce jumping and suit their shy nature.
Diet
Marbled hatchetfish are surface-feeding micropredators built to take food from the very top of the water and just above it, so foods must float or be presented at the surface. Offer floating flake and small floating pellets, but lean heavily on live and frozen foods such as wingless fruit flies, mosquito larvae, daphnia, baby brine shrimp, and small bloodworm, which suit their natural diet of insects taken at and above the surface. They generally ignore food that sinks past them.
Feed small amounts once or twice a day and watch that the food stays accessible at the surface. Live insect foods like fruit flies are excellent and bring out natural feeding and leaping behavior. A varied surface diet keeps them in good condition and supports their fast metabolism.
Behavior & temperament
Marbled hatchetfish are peaceful, shy, and strongly shoaling, and must be kept in a group of at least six, ideally more, so they feel secure and stay out in the open near the surface. They are excellent community fish for calm, soft-water setups, mixing well with small tetras, rasboras, pencilfish, corydoras, and dwarf cichlids that occupy the lower levels; avoid large, boisterous, or surface-competing tankmates. They occupy the very top of the tank that most community fish ignore, making them a useful 'top dweller'.
Kept in too small a group or with rowdy tankmates they become nervous and jumpy, both literally and figuratively. Enrichment comes from floating plants, shade, calm water, and a confident shoal, which encourage natural surface schooling and occasional spectacular leaps after food. They are a peaceful, fascinating choice for a well-covered blackwater community.
Health
The most common cause of loss is simply jumping out of the tank, so a fully sealed lid with no gaps is the top priority. Beyond that they are moderately sensitive fish susceptible to ich (white spot), bacterial and fungal infections, and stress when kept in unstable water, hard alkaline conditions, or too small a group; wild-caught imports can arrive thin and need careful settling and feeding. Their surface-feeding habit means they can be outcompeted or go hungry if food does not stay at the top.
Prevent problems with a sealed tank, soft warm stable water, floating cover, an adequate shoal, surface-presented foods, and quarantine of new arrivals, which are often wild-caught. Watch for white spots, clamped fins, thinness, lethargy, or labored breathing, and consult an aquatic veterinarian before medicating. This information is general guidance and not a substitute for advice from a qualified aquatic veterinarian.
Tips, DIY & hacks
Seal every gap in the lid, including cutouts for filters and cords, because these fish will escape through the smallest opening. Keep a shoal of six or more, feed floating and live insect foods like wingless fruit flies, and use floating plants and blackwater conditions to keep them calm and feeding confidently.