Blackwing hatchetfish
Carnegiella marthae
Also known as Marthae Hatchetfish
FreshwaterFish
Care at a glance
- Temperature
- 68–82°F
- 20–28°C
- pH
- 5.5–7.0
- Adult size
- 1.4 in
- 3.5 cm
- Minimum tank
- 30 gal
- 115 L
- Temperament
- Peaceful
- Social behavior
- Shoaling
- Swim level
- Top
- Difficulty
- Medium
- Breeding
- No record
- Rarity
- Very rare
- Family
- Gasteropelecidae
- Origin
- Venezuela, Brazil
Overview
Keep at least six together in a tank of roughly 115 liters with plenty of surface area, and always use a tight lid. They sit right at the top and eat from the surface, so offer floating flake, small frozen foods, and live items like fruit flies or mosquito larvae. Keep them warm in the mid 20s C with soft, acidic to neutral water. They're peaceful and best with calm tankmates.
In the wild
Blackwing hatchetfish live in slow tributaries and floodplain pools of the Amazon, mostly in Brazil and Venezuela. The water is soft, acidic, and stained dark with tannins, with floating plants and roots up top where these fish stay. They want surface cover and very still water, so floating plants and a gentle filter outflow help a lot.
Good to know
This is a small hatchetfish in the family Gasteropelecidae, reaching about 3.5 cm. The deep, keel-shaped chest houses the muscles that power its oversized pectoral fins. Captive breeding is rarely recorded. The IUCN lists it as Least Concern.
Did you know
Hatchetfish are true flyers, not gliders. They beat those wing-like pectoral fins fast enough to break the surface and travel a short distance through the air, usually to escape something chasing them. That's exactly why a lid is non-negotiable.
Weekly picks
Tank mates
Blackwing hatchetfish is a peaceful, shoaling species that keeps to the top. These picks share a community profile with it, are safe together in both directions, and overlap on water type, temperature and pH.

Upside-down catfish
Synodontis nigriventris
Freshwater3.9 in (10 cm) · 30 gal (115 L)75–82°F (24–28°C)
Altus tetra
Brachypetersius altus
Freshwater2.6 in (6.5 cm) · 30 gal (112 L)73–82°F (23–28°C)
Redfin halfbeak
Nomorhamphus ebrardtii
Freshwater3.5 in (9 cm) · 29 gal (110 L)75–81°F (24–27°C)
Panama hoplo
Hoplosternum punctatum
Freshwater3.1 in (8 cm) · 30 gal (115 L)72–79°F (22–26°C)
Australian rainbowfish
Melanotaenia fluviatilis
Freshwater4.3 in (11 cm) · 30 gal (115 L)68–77°F (20–25°C)
Common hatchetfish
Gasteropelecus sternicla
Freshwater1.6 in (4 cm) · 33 gal (125 L)68–82°F (20–28°C)
Common questions
What size tank does a Blackwing hatchetfish need?
A Blackwing hatchetfish needs at least 30 gal (115 L). It spends most of its time in the top.
What temperature and pH does a Blackwing hatchetfish need?
A Blackwing hatchetfish is comfortable at 68–82°F (20–28°C) with a pH of 5.5–7.0.
How big does a Blackwing hatchetfish get?
An adult Blackwing hatchetfish reaches about 1.4 in (3.5 cm).
Does a Blackwing hatchetfish need a group?
Yes. A Blackwing hatchetfish is a shoaling species and should be kept in a group, not singly.
Related species
1.6 in (4 cm)32 gal (120 L)68–82°F (20–28°C)Marbled hatchetfish
Carnegiella strigata
1.6 in (4 cm) · 32 gal (120 L)
1 in (2.6 cm)14 gal (54 L)73–82°F (23–28°C)Scherer's hatchetfish
Carnegiella schereri
1 in (2.6 cm) · 14 gal (54 L)
1 in (2.5 cm)26 gal (100 L)73–79°F (23–26°C)Pygmy hatchetfish
Carnegiella myersi
1 in (2.5 cm) · 26 gal (100 L)
1.4 in (3.5 cm)30 gal (112 L)73–82°F (23–28°C)Silver hatchetfish
Gasteropelecus levis
1.4 in (3.5 cm) · 30 gal (112 L)
1.6 in (4 cm)33 gal (125 L)68–82°F (20–28°C)Common hatchetfish
Gasteropelecus sternicla
1.6 in (4 cm) · 33 gal (125 L)
3.5 in (9 cm)26 gal (100 L)73–82°F (23–28°C)Spotfin hatchetfish
Thoracocharax stellatus
3.5 in (9 cm) · 26 gal (100 L)
