The Black-Winged Hatchetfish, known scientifically as Carnegiella marthae, is a unique and fascinating species within the freshwater aquarium hobby. Originating from the densely forested river basins of South America, specifically in regions like Venezuela and Brazil, this small fish is renowned for its distinctive body shape and behavior. The hatchet-shaped body, which gives the hatchetfish its common name, is adapted for a life spent predominantly at the water's surface, where it feeds and interacts with its environment.

One of the most striking features of Carnegiella marthae is its dark, almost black dorsal area, which contrasts sharply with the silvery hues of its ventral side. This coloration not only provides the Black-Winged Hatchetfish with camouflage against predators from above and below but also makes it a visually appealing addition to the top levels of the aquarium, a region often less occupied by other species.

Black-Winged Hatchetfish are known for their peaceful nature and are best kept in groups due to their schooling behavior. This not only helps to reduce stress among individuals but also creates a more natural and engaging display as they move synchronously just below the water surface. Their gentle temperament makes them suitable tank mates for other peaceful species, though care should be taken to house them with fish that do not view them as prey due to their small size.

The diet of the Black-Winged Hatchetfish primarily consists of small insects and other invertebrates in their natural habitat. In captivity, they should be provided with a variety of foods, including finely chopped live or frozen foods such as brine shrimp and daphnia, as well as high-quality floating pellets and flakes designed for surface feeders. This diet helps mimic their natural feeding habits and ensures they receive the nutrients needed for health and vitality.

Breeding Carnegiella marthae in captivity can be challenging, with successful breeding requiring specific conditions that mimic their natural habitat, including soft, acidic water and a well-planted aquarium that offers plenty of hiding spots for fry. The reproductive habits of Black-Winged Hatchetfish are not well documented, making breeding attempts a venture for more experienced aquarists.

Caring for Black-Winged Hatchetfish requires attention to their specific needs, particularly regarding their preference for living near the water's surface. The aquarium should be securely covered, as these fish are skilled jumpers and may leap out of the tank if startled or in search of food. Providing a calm environment with gentle water flow and avoiding aggressive or overly active tank mates will help ensure their well-being.

In summary, Carnegiella marthae offers a unique opportunity to observe and care for a species that occupies the upper layers of the aquarium, adding diversity and interest to the community tank. Their care, while requiring a focus on specific dietary and environmental needs, rewards the dedicated aquarist with the beauty and graceful surface activity of these remarkable fish.