Black-winged Hatchetfish

Geographic Origin and Biotope: Rio Negro and Orinoco basin. Populates the upper reaches of dark forest rivers, lagoons surrounded by dense riparian vegetation and flooded igapò forests.

Taxonomy and Morphology: Black-winged Hatchetfish (Carnegiella marthae). Tiny hatchet-shaped characin. Possesses highly developed pectoral musculature able to vibrate the fins at very high speed, using them for swimming or to take real flights over the water.

Social Behavior: Absolutely schooling and stationary on the surface. In small groups they wear themselves out with stress. Needs 10 specimens or more. They live constantly in the top 2-3 cm (1 inch) of water.

Coloration and Sexual Dimorphism: Silvery translucent body crossed by a lower dark stripe. The common name (Black-winged) derives from the lower margin of the enormous pectoral fins, heavily marked with black. Females seen from above are stockier.

Aquarium Setup: 60 cm (24 inches) aquarium. MANDATORY LID: they literally fly to escape predators or catch midges. Create directional surface currents with the pump to imitate a stream. Floating plants indispensable to prevent them from feeling exposed.

Diet and Feeding: Surface micro-insectivore. Since the mouth is facing upwards, it will ignore sunken food. Provide live Drosophila (wingless fruit flies), finely chopped floating flakes and freeze-dried bloodworms.

Water Quality: Prefers pure Blackwater: acidic (pH 5.0-6.5) and very soft waters, added with tannins (Catappa leaves, alder cones). Extremely intolerant to ammonia spikes.

Compatibility and Tankmates: Unsuitable to coexist with overly voracious fish that compete on the surface or with restless fish (e.g. giant Danios) that induce panic jumps. Excellent with Corydoras, Otocinclus, dwarf Tetras and Apistogramma.

Aquarium Reproduction: Rare. Requires very dark water and simulated temperature drops. The eggs (non-adhesive) are released on the surface and sink among the plants. Tiny fry require infusoria on the first day of free swimming.

Risks and Diseases: Death from jumping out of the tank or from nocturnal impact against the lid's fluorescent tubes is very high. It is prone to Ich parasitosis if temperatures drop drastically.