Thoracocharax securis – Giant Hatchetfish
Thoracocharax securis was first described by De Filippi in 1853. The fish belongs to the family Gasteropelecidae (Hatchetfishes). Their common name is Giant Hatchetfish. A name that , by the way, is also sometimes used for Gasteropelecus maculatus.
The genus name Thoracocharax is a combination of the Greek words “thorax” (breast) and “charax” (sharp edge or point), referring to the distinctive, sharp shape of the body. The species name securis is Latin for “axe” or “hatchet,” also referring to the characteristic shape of the body.
Synonyms for Thoracocharax securis are: Gasteropelecus pectorosus and Gasteropelecus securis.
Description, Behavior and Life Expectancy
Thoracocharax securis, also known as Giant Hatchetfish, has a distinctive convex body, meaning the body is strongly curved upward. The back is relatively straight. The pelvic fins are small. Most distinctive are the large, transparent pectoral fins that resemble wings and can cover up to half the body length. The color is predominantly silvery white to white, with an olive-brown back. Depending on the light, the color may appear iridescent green or blue. A vertical green to yellow stripe runs from the gill cover to the base of the tail. The head is darker in color than the flanks. Specific patterns or markings are not described in detail in the linked documents. The fins are translucent, with possibly some dark pigmentation on the anterior rays of the dorsal fin. The fish grows to about 9 cm in length.
Sex differences: It is difficult to distinguish clear physical differences between males and females. Adult females may be slightly fuller bodied, especially when carrying eggs. Behavioral differences between the sexes are not described.
Behavior and Temperament: Thoracocharax securis is a peaceful fish that prefers to be kept in groups of at least six, but preferably ten or more. They are shy and live in the upper and middle water layers of the aquarium. They are not bottom dwellers. It is essential to keep them with small, non-aggressive tank mates, such as certain tetras, pencilfish, Corydoras, dwarf cichlids (such as Mikrogeophagus or Apistogramma), and smaller species of sucker catfish. Avoid large, fast or aggressive fish. The fish is an agile jumper and can jump up to 2.7 meters out of the water. A well-sealed aquarium is therefore essential.
Life expectancy: The life expectancy of Thoracocharax securis in the wild is unknown. In an aquarium, they can live up to 5 years.
Habitat and Ecology
Thoracocharax securis is native to Brazil and Peru. In these countries, they live mainly in the Amazon basin, including the Rio Nanay in Peru and the Orinoco and Paraná rivers in Brazil. The fish is a river fish that lives in slow-flowing, soft-water ecosystems. They are found in the upper water layers of rivers and streams, with a preference for areas of dense overhanging vegetation.
Their natural habitat is characterized by an abundance of underwater vegetation, including fallen branches, root systems and leaf litter. The banks of the water are often covered with trees, providing shade and shelter. The bottom consists of a mixture of organic material, such as leaves and branches, and possibly sand or mud.
Thoracocharax securis lives in a tropical climate with seasonal variation in water levels. There are periods of floods and droughts, depending on the rainy season.
Diet
In the wild, Thoracocharax securis feed mainly on small insects and their larvae, which they catch at the water surface. Their diet may also include other small invertebrates.
In an aquarium, the fish can be fed a varied diet of high-quality dry food (flakes or pellets), supplemented with live or frozen food such as: small insect larvae (for example, mosquito larvae or fruit flies), daphnia, cyclops and artemia. A small amount of quality flake food can also be offered. It is important not to overfeed the fish, as this can lead to water pollution. The food should be eaten quickly and any leftovers should be removed.
The Aquarium
For a group of at least six, but preferably ten or more, Thoracocharax securis requires an aquarium of at least 150 liters . For larger groups , the aquarium volume should be increased accordingly. The aquarium should be well sealed to prevent the fish, which are agile jumpers, from jumping out of the water .
The décor should mimic the fish’s natural habitat. Use a dark background and plant the aqu arium densely with floating plants and other plants that create shaded areas. The plants should also provide shelter. A substrate of fine sand is suitable. Avoid sharp objects. Rocks are not essential, but can be added if they fit the overall decor.
The ideal water values are a pH of 6.0-7.5, a GH of 5-15 and a temperature of 23-30°C. Regular water changes (25% per week) and good filtration are essential.
Suitable co-inhabitants are small, peaceful fish such as certain tetras, pencil fish, Corydoras and the like, dwarf cichlids (such as Mikrogeophagus or Apistogramma), and smaller species of catfish. Avoid large, fast or aggressive fish that might stress or attack Thoracocharax securis.
Breeding
Not much is known about the breeding of this species. Breeding in captivity is difficult.
Conclusion
Thoracocharax securis, the Giant Hatchetfish, is a fascinating fish with a unique body shape and striking jumping ability. Although peaceful and relatively easy to care for in terms of water parameters, the species does require specific setup and a group of at least six specimens to avoid stress. Its shy nature and jumping ability require a well-enclosed aquarium with dense vegetation. The lack of successful breeding attempts in captivity indicates a higher degree of difficulty for experienced aquarists.
Available information suggests that Thoracocharax securis is not a suitable fish for beginners. The combination of specific water parameters, the need for a large group, the shy nature and jumping ability make keeping this species challenging. The lack of detailed information on captive breeding emphasizes the need for further research and experience for successful keeping. The striking body shape and jumping ability are unusual characteristics that make this fish an interesting, but demanding, addition to an aquarium.
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Author
John de Lange
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Frequently Asked Questions
How large does Thoracocharax securis become?
This species can reach a length of about 6 to 7 centimeters.
What is the behavior of Thoracocharax securis in an aquarium?
Thoracocharax securis is a peaceful and shy fish that resides mainly in the upper water layer. They are excellent jumpers, so a well-covered aquarium is essential. They are most comfortable in a shoal of at least six conspecifics
What water values are ideal for Thoracocharax securis?
They thrive best with a water temperature between 24 and 28°C, a pH of 5.5 to 6.5 and a water hardness of 4 to 18 dH.
What do Thoracocharax securis eat?
In the wild, this fish feeds on small insects and crustaceans on the surface of the water. In the aquarium, it accepts live food such as fruit flies and black mosquito larvae, as well as floating dry food.
How can I best house Thoracocharax securis?
An aquarium at least 100 cm long is recommended, with sufficient swimming space at the surface. Use floating plants to dampen bright light and provide a tightly sealed lid to prevent escape.
Is Thoracocharax securis suitable for a community aquarium?
Yes, if kept with other peaceful fish that are not too active. They can be skittish, so avoid combining with aggressive or very active species.
Can Thoracocharax securis jump?
Yes, this fish is known for its jumping ability and can jump out of the water, especially when startled. A well-covered aquarium is therefore necessary.
How to breed Thoracocharax securis?
Breeding is challenging. A separate breeding tank with soft, acidic water (pH around 6) and dim lighting is required. The eggs are deposited among plants and hatch after about 30 hours. The young swim freely after five days and must be fed with infusions.
How old can Thoracocharax securis get?
With proper care, these fish can reach an age of 4 to 5 years.
