About the Silver Hatchetfish
Species Type: Freshwater Fish
Care Level: Moderate. May tolerate only a narrow range of water parameters, have specific dietary requirements including frozen or even live foods, may have behaviors that severely limit potential tankmates or may require a specialized aquarium setup.
Origin: Brazil, southern tributaries of the Amazon; Guyana, Suriname.
Compatibility/Temperament: Peaceful surface fish; it can be nervous and prone to jump if kept in tanks with active lower-water fish. Floating plants are mandatory; hatchetfish frequently lie motionless among the plants.
Silver Hatchets, also known as the Common Hatchetfish, are among the more uniquely shaped species of fish. Hatchetfish have a slender body with a deep "belly" and pectoral fins that are set high on the body and attached to very powerful muscles. These fins propel the fish from the water, enabling it to glide considerable distances through the air. Studies by Francine Weist (1995) concluded that the pectoral fins are not moved during this "flight" but are used as a powerful thruster to propel the fish from the water as well as to prevent the fish from diving too deeply upon its return to the water [reported in Weitzman & Palmer, TFH, September 1996].
These fish are avid jumpers and should have a well-covered tank, and during aquarium maintenance the tank should be covered as much as possible as they will take any advantage to jump out. Hatchetfish have upturned mouths characteristic of true surface dwellers.
Hatchetfish occur in slow flowing forest streams, usually thick with surface vegetation. It quickly jumps clear of the water when threatened from below, and probably also to catch flying insects. They live in large shoals, and should be maintained in groups of six or more fish. They are extremely peaceful and well suited to a community aquarium of small quiet fish like tetras and rasbora, discus, and dwarf cichlids.
The family Gasteropelecidae contains three genera. Thoracocharax, the most primitive and distinguished by its impressive keel, contains two species, T. securis and T. stellatus. Gasteropelecus contains two species, G. sternicla and G. maculatus, although G. levis is possibly a third species [Weitzman, 1996]. These two genera contain the largest of the hatchetfish, and all are silver in colouration; G. sternicla is the more frequently seen of these five species, though any of them are frequently offered as "Silver Hatchetfish." The third genus, Carnegiella, contains four species that are the most derived or specialized of the hatchetfishes. Weitzman & Palmer hypothesize on the basis of their anatomy that these three genera had a common ancestor in the distant past that was related to some other characiform subgroup.
Silver Hatchetfish Diet
Primarily feeds on insects on or that land on the water surface; only floating foods are suitable. Will accept prepared floating foods; small insects like wingless fruit flies are ideal.
Up to 2.5 inches; G. maculatus, a similar species, attains 3.5 inches.
Minimum Tank Suggestion
24 inches in length
Ideal water parameters for Silver Hatchetfish
Soft (hardness under 15 dGH), slightly acidic (pH 6.0 to 7.0) water, temperature 23-27C/73-81F.