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Fish

Blackwing hatchetfish

Carnegiella marthae
French name : Poisson-hachette de Marthae

The blackwing hatchetfish is a tiny, deep-chested surface dweller from the blackwater tributaries of the Rio Negro and Orinoco. It cruises the top few centimetres of the water column and is a confirmed jumper, so a tightly fitting lid is essential. Keep it in a shoal of at least eight, as isolated individuals become stressed and reclusive. It thrives in warm, very soft, acidic water rich in tannins, ideally over a dim, well-planted blackwater setup with floating cover and gentle flow. Peaceful and easily intimidated, it suits calm tankmates such as small tetras, pencilfish and Corydoras. Feed small floating and surface foods: fine flake, tiny live or frozen insects, fruit flies and micro-crustaceans. Best reserved for aquarists able to maintain stable soft-water chemistry.

Water
Freshwater
Origin
Rio Negro and upper Orinoco basins, South America
Adult size
3.5 cm
Diet
Omnivore
Temperament
Peaceful
Difficulty
Intermediate
Keep in group of
8+
Blackwing hatchetfish (Carnegiella marthae)
Illustration

Water parameters

Temperature23 – 29 °C
pH4.5 – 6.5
Carbonate hardness (KH)0 – 4 °dKH
General hardness (GH)1 – 8 °dGH

Tank & stocking

Minimum tank volume60 L
Volume budget per individual 5 L — adds up with tank-mates
Minimum group size8 individuals (shoaling)

“Minimum tank volume” is a reasonable floor, not an absolute limit. The per-individual budget is used by the Aqua app to estimate how heavily a tank is stocked.

Frequently asked questions

What size aquarium does Blackwing hatchetfish need?

Provide at least 60 litres for a small group to keep Blackwing hatchetfish in good conditions.

What water parameters does Blackwing hatchetfish need?

A temperature of 23–29 °C, pH 4.5–6.5.

Is Blackwing hatchetfish peaceful or aggressive?

Its temperament is peaceful.

What does Blackwing hatchetfish eat?

Its diet: omnivore.

How many Blackwing hatchetfish should be kept together?

It is a social species: keep a group of at least 8.

How big does Blackwing hatchetfish get?

Around 3.5 cm as an adult.

Is Blackwing hatchetfish suitable for beginners?

Care level: intermediate.

Planning a tank with Blackwing hatchetfish?

AquaTender turns these parameters into live advice: it checks whether your tank is big enough, how heavily it's stocked, and whether your fish are compatible — then tracks water tests, photos and maintenance for you.

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Fish from the same biotope

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