Blackwing Hatchetfish

About

The blackwing hatchetfish is the blackwater specialist of the genus, and a smaller, fussier fish than the marble hatchetfish this library already carries. Seriously Fish records the largest officially measured specimen at 28.1 mm standard length, against about 35 mm for Carnegiella strigata; FishBase gives 2.9 cm SL with aquarium fish reaching 3.5 cm total length. Where the marble hatchetfish is patterned with the mottling it is named for, C. marthae is a silvery fish with a dark line along the flank and dark markings on the wing-like pectoral fins that give it its name. It lives in the upper Orinoco in Venezuela and the rio Negro in Brazil, in igapó and igarapé blackwater that Seriously Fish describes as 'typically acidic, of negligible carbonate hardness and conductivity and stained brownish' - which is why FishBase gives it pH 5.5-6.5 and 0-4 dH where our marble hatchetfish entry, following the same sources for C. strigata, runs to pH 7 and 12 °dGH. Now the jumping, because the usual story is wrong in an interesting way. Hatchetfish do not fly. Seriously Fish cites Wiest (1995), who filmed them at high speed and found the pectoral fins are used to leave the water but not while the fish is in the air, so 'the action is more accurately described as a powerful jump and is actually a modified threat response'. The same researcher found they can only jump once or twice before needing to rest, and collectors report gasteropelecids rarely jumping by day even when chased with a net. But the profile is blunt about the dark: 'during darkness the fish do jump, and leaving the cover open even slightly can result in one or more hatchetfish on the floor by morning.' The gap-free lid is not optional - it is just needed for a different reason than the shop label suggests.

Care

Ten or more - Seriously Fish says buy as many as possible - in a heavily planted tank from 60 litres with at least 60 cm of surface, floating plants to hang under, a dark substrate, leaf litter and gentle to moderate flow. 24-27 °C, pH 5-6.5, hardness 1-10 °dGH with negligible carbonate hardness: this is a soft-water fish, and hard Lithuanian tap water needs cutting with RO or rainwater before it is a fair home, which is what makes it a step up from the marble hatchetfish rather than a swap for it. Seriously Fish calls it 'very peaceful but does not make an ideal community fish due to its small size and rather timid nature' - keep it with similarly small, calm characids and small callichthyid or loricariid catfish, or as a dither fish over Apistogramma, and never with anything that hunts the surface. Cover every gap in the lid, cable cut-outs included, because they jump at night.

Diet

Surface micropredator taking small invertebrates from the film. Suitably small dried food is accepted, but regular Artemia nauplii, Daphnia, Moina and grindal worm are what keep it in condition. Sinking food never reaches it.

Telling males from females

What works for this species, most reliable first.

• Belly depthA hint only · only on well-fed adults, and only as a comparison

  For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.

Also in these lists

Similar species

Same category and the closest water parameters — if this species isn't quite it, start here.

Sold in Lithuania

These Lithuanian shops listed this species in their public catalogue (checked August 8, 2026). Stock moves — ask before you travel.

These links are unpaid: we get nothing for them and ask for nothing.

Frequently asked questions

What tank size does a Blackwing Hatchetfish need?

A Blackwing Hatchetfish needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Blackwing Hatchetfish need?

Blackwing Hatchetfish does best at 20–28 °C (68–82.4 °F), pH 4–7 and a general hardness of 1–10 °dGH.

What group size does a Blackwing Hatchetfish need?

Blackwing Hatchetfish is a social species — keep a group of at least 10 so natural behaviour emerges and stress stays low.

Is the Blackwing Hatchetfish suitable for beginners?

Blackwing Hatchetfish is a demanding species best attempted with some experience — it needs stable, closely watched conditions to thrive.

Sources

• Seriously Fish — Carnegiella marthae (Blackwing Hatchetfish)
• FishBase — Carnegiella marthae (Blackwinged hatchetfish)
• Wikipedia — Black-winged hatchetfish