Marbled Hatchetfish Silver (Carnegiella marthae)

Carnegiella marthae is one of the smallest hatchetfish species, native to the upper Amazon basin tributaries and Orinoco River system in Venezuela, Colombia, and Peru. It is closely related to and often confused with C. strigata (Marble Hatchetfish), but C. marthae has a distinctly less elaborate pattern — typically showing a dark horizontal stripe along the flanks against a pale silver body, with dusky fin markings.

The characteristic deep, laterally compressed, hatchet-shaped body profile is fully expressed in C. marthae — the same dramatically deep ventral keel and enlarged pectoral fin musculature that defines the hatchetfish family (Gasteropelecidae). The pectoral fins can vibrate at high speed, enabling brief surface-skimming escape behavior when threatened — hence the importance of secure aquarium lids.

C. marthae reaches only 3–4 cm, making it the smallest of the three Carnegiella species commonly available. Its reduced size makes it appropriate for slightly smaller aquariums than C. strigata, though a tight lid and appropriate group size remain essential.

In the wild, C. marthae inhabits the surface film of slow-moving blackwater streams and pools in heavily vegetated forest environments, feeding primarily on small invertebrates, insects, and organic particles that fall onto the water surface from overhanging vegetation.

Carnegiella marthae requires soft, acidic blackwater conditions: pH 5.0–6.5, hardness 1–5 dGH, and temperatures 24–29°C. They are sensitive to water quality deterioration and require pristine conditions with very low nitrate levels.

A minimum 60-liter aquarium with abundant floating plants (Salvinia, Frogbit) and surface cover suits a group well. Surface area is more important than depth — a longer, shallower aquarium is better than a tall one. A secure, tight lid with no gaps is mandatory — hatchetfish can jump considerable distances.

Feed exclusively at the surface with floating micro pellets, surface flake, freeze-dried daphnia, fruit flies, and live or frozen tiny invertebrates that drift at the surface. They will not feed at lower depths.

Compatible with small, gentle, lower-dwelling species: nano rasboras (mid-water), pygmy corydoras (bottom), and other peaceful species that do not compete at the surface. Avoid boisterous or aggressive fish.

Keep in groups of at least 8 for security and natural surface-skimming schooling behavior. Frequent small water changes (20% twice weekly) with temperature-matched RO or soft water maintain the acidic, soft conditions required.