Name: River Hatchetfish
Other Name: Silver Hatchetfish, Common Hatchetfish
Scientific Name: Gasteropelecus sternicla
Distribution: Peruvian and middle Amazon basins, Guianas, Venezuela
Length: 1.5" in the wild, 2.5" in the aquarium
Diet: Insects, worms and crustaceans resting on or flying above the water in the wild. Live foods and high-protein flakes and pellets in captivity.
Water Temperature: 73 to 81 degrees Fahrenheit (23-27 degrees Celsius)
Water Chemistry: Moderately hard water is fine; they can be acclimated to just about any water hardness value.
Lifespan: 5 years
Species Description These are convex silvery fish with straight khaki-colored backs and lateral compression. The ventral fins are small but the pectoral fins are very long and transparent. They work like wings for gliding purposes. They have a small upturned mouth (which shows that they eat small foods from the surface). There is a black stripe extending from the gill cover to the caudal peduncle.
Species Behaviour Have the tank fully-covered! These fishes are quite nervous and great jumpers. Innumerable hatchetfishes have jumped to their deaths because of nervousness (or ostensibly because they are trying to prey upon terrestrial insects).
They are peaceful yet active and do best in the company of conspecifics. A shoal of six or more will make them somewhat calmer but they should still be kept as if they will jump at any moment.
Natural Conditions Slow-moving creeks and swamps
Natural Range Peruvian and middle Amazon basins, Guianas, Venezuela
Minimum recommended tank size 25-30 gallons
Water Temperature 73 to 81 degrees Fahrenheit (23-27 degrees Celsius)
Water Quality They can take slightly acidic to slightly alkaline waters (pH between 6 and 7.5) and moderately hard water (but they can be acclimated to almost any range of hardnesses).
Sexing The difference can only be told by the eggs held by ready-to-breed females.
Breeding Has apparently occured in captivity though details on the event are sketchy at best.
Feeding Insects resting on or flying above the water in the wild. Live foods and high-protein flakes and pellets in captivity.
Miscellaneous Info One of the easiest hatchets to care for in captivity but they don't breed all that easily in aquarists' tanks, if they have at all!