Hatchetfish, whilst not the most colourful of fish, have a unique nature and appearance, creating a welcome contrast and focal point. The fish are peaceful, small, and interesting to observe, and on the condition that your tank provides safe surroundings, make excellent community fish.
The hatchetfish family (Gasteropelecidae) is part of the Characin group of fish, which includes the Tetras, Pencilfish, and Piranhas amongst others. The family can be split into three groups (genera) Carnegiella, Gasteropelecus, and Thoracocharax, with only a few species in each group.
Carnegiella sp.The Carnegiella group contains the smallest fish, and C. myersi is the smallest of all the hatchetfish, growing to no more than an inch (2.5cm) but is rarely seen for sale. This tiny fish also has the most transparent body with few markings except for a light speckling and darker topside.
The Black-Winged Hatchetfish C. marthae marthae, which occasionally turns up in batches of other hatchetfish as well as on sale as a species, is not much bigger and grows to around 3.5cm. The name comes from the darkened pectoral fins and black line along the underside of the body and whilst an interesting fish, this species is sensitive to water conditions and will only thrive in soft, acidic water.
The most popular of this group is the Marbled Hatchetfish C. strigata, and is also the most patterned, sporting black/brown broken patches on a silver body. There are two variations of this species; one has more silver with lighter marks whilst the other has more solid black markings. Both variations grow to around 4cm and although they prefer softer water, will do well up to a pH of 7.5 and medium-hard water providing they are well acclimated.