Minimum Tank Size: 20 Gallons (76 Liters)
Care Level: Moderately Difficult
Water Conditions: 5.5-7.0 pH and Soft to Moderately Hard Water
Temperature: 75-84 °F (24-29 °C)
Maximum Size: 1.5 inches (3.5 cm)
The black-winged hatchetfish (Carnegiella marthae) is a small, peaceful freshwater fish, noted for its unusual body shape. Its laterally compressed body resembles the head of a hatchet, and actually gave rise to its name – the hatchetfish.
These fish primarily inhabit slow moving streams and ponds, and are also found in Igarapes – shallow, dark waterways, where little light reaches the surface. The waters they inhabit are very soft, with virtually no carbonate hardness, and they usually have a brownish tinge to them – though this disappears when the tributaries reach the rivers.
They are endemic to Brazil and Venezuela, and are found in the Orinoco and Negro regions. There are some reports that they have also been found in Columbia, but there appears to only be one account of them being discovered that far west at the extreme edge of the Orinoco region.
Black-winged hatchetfish stay relatively small in the home aquarium, and can reach a maximum length of 1.5 inches (3.5 cm). Unfortunately, these fish have one of the shortest life spans of any hatchetfish in the hobby, and usually only live for around two years in the home aquarium.
Black-winged hatchetfish are a schooling fish, and should always be kept in groups of at least 6. But with that being said, they seem to be healthier and more active when kept in larger groups, so it’s usually best to aim for groups of 8 or more when keeping these fish.
A 20 gallon fish tank is adequate for keeping a small school of these fish – though it should always be wide and not tall – since these fish spend nearly all of their time congregated near the surface.
It can’t be stated strongly enough that any aquarium containing these fish must be covered. They are noted jumpers, and in the wild they leap out of the water to catch flying insects. They are also capable of leaping several feet out of the water when threatened, so if a tank is left uncovered, it won’t be long before fish start to appear on the floor around the aquarium.
These fish make an excellent addition to most community fish tanks, and while they may direct some aggression at others of their own species, they are rarely ever aggressive towards other fish. As they spend most of their time near the surface, their tank mates should ideally inhabit other parts of the tank. Some good tankmates for them are corydoras catfish, or any of the smaller tetras.
Any aquarium containing these fish should replicate their natural habitat as closely as possible. They are usually found in dark, heavily vegetated waterways, with the bottom resembling a maze of trees roots, fallen branches, and leaf debris.
Their tank should mimic this as closely as possible, and this can be accomplished through adding floating plants, bogwood, driftwood, a dark substrate, and even leaf litter if a clean source of leaves is available. Make sure the leaves haven’t been exposed to pesticides or herbicides before placing them in the aquarium.
When choosing a filter, a hang-on-back filter is usually the best choice. Not only are they economical, but if a person chooses a reliable and efficient filter like the Aquaclear Power Filter, it will keep their water sparkling clean. I’ve used an Aquaclear Power Filter for years without incident, and they are used on the majority of my tanks (with some of the larger tanks using canister filters).
Black-winged hatchetfish are predators in the wild, with upwards of 90% of their diet being composed of flying insects and crustaceans. But they are still omnivores, and they can adapt well to prepared foods in a home aquarium.
However, as many of them are live-caught, it may take them some time before they start to accept prepared foods. If they are reluctant to eat the food they are offered, then it should be mixed in with live or frozen insects and crustaceans. Over time, they will come to accept dry fish food.
One of the best choices for fish food is Hikari Semi-Floating Micro Pellets. Not only are they perfect for these fish’s small mouths, but they also float near the surface – right where these fish feed.
While prepared foods can satisfy most of the dietary needs, their diet should still be regularly supplemented with live or frozen foods. Some of the best live foods to offer them are mosquito larvae (illegal to culture in some areas), wingless fruit flies, daphnia, and brine shrimp. It’s best to limit live food to ones that will remain close to the surface of the water, where these fish spend most of their time.
Their preferences remain virtually the same with frozen foods, and the most commonly accepted and available frozen foods are brine shrimp, bloodworms and daphnia. Make sure to let the food thaw out in a small cup of tank water before feeding it to these fish.
It can be relatively difficult to sex these fish, but the adult females are more round-bodied than the males.
While other hatchetfish (marbled hatchetfish) have been bred in the home aquarium, at this time, there are no reliable accounts of black-winged hatchet fish being bred.