Marbled Hatchetfish

Geographic Origin and Biotope: Amazon and Orinoco Basin (Peru, Colombia, Brazil, Guyana). Inhabits forest streams, flooded areas (igapó) covered by thick floating foliage and the calm banks of major rivers.

Taxonomy and Morphology: Marbled Hatchetfish (Carnegiella strigata). Characin with a very particular "hatchet" shape, with a deeply keeled belly and an almost flat back. Reaches 4 cm (1.5 inches). Hypertrophic pectoral fins pointing upwards.

Social Behavior: Extremely gregarious and strictly confined to the top inches of surface water. Hovers against the current waiting for insects. Lives constantly in terror of underwater predators, requiring schools of at least 8-10 individuals to feel secure.

Coloration and Sexual Dimorphism: Silvery or pale golden background crossed by a spectacular network of dark marbled stripes (strigata = striped) on the belly. Mature females have a slightly more convex dorsal profile due to eggs.

Aquarium Setup: Minimum 80 cm (32 inches) in length. A LID IS A VITAL REQUIREMENT: they are designed to fly for meters out of the water. Insert abundant floating vegetation (Limnobium, Pistia) and create a moderate but constant surface flow.

Diet and Feeding: Exclusive surface micro-insectivore. Categorically refuses any food that sinks. Feed fruit flies (Drosophila), floating freeze-dried bloodworms and very small flakes placed on the water's surface.

Water Quality: Pure Amazonian fish: demands warm (24-28°C / 75-82°F), moderately acidic to neutral (pH 5.5-7.0) waters of low or moderate hardness. Very sensitive to spikes in nitrogenous compounds.

Compatibility and Tankmates: Completely inoffensive and vulnerable. Ideal companion for peaceful Tetras, Corydoras, Otocinclus and Loricariids. Avoid overly lively surface species (e.g. Giant Hatchetfish or large Danios) or medium-large cichlids.

Aquarium Reproduction: Rare. Requires very soft (osmosis) and acidic water, with a rich live diet. They scatter tiny, non-adhesive eggs among the roots of floating plants. No parental care.

Risks and Diseases: In addition to the fatal risk of jumping, they suffer from thinning due to food competition if they fail to grab the floating fragments before they sink. Frequent carriers of Ich post-importation.