Giant Hatchetfish

Geographic Origin and Biotope: Vast distribution across the main Amazon River system in Brazil and Peru. Prefers expansive, quiet lagoons, flooded oxbows, and slow rivers, schooling under the thick canopy of coastal trees and fallen wood.

Taxonomy and Morphology: The absolute giant of the Gasteropelecidae family. Thoracocharax (meaning 'armored characin') easily reaches 8-9 cm (3.5 inches). The abdominal keel is so deep and massive it almost looks unnatural, comprising the vast majority of the fish's profile. Exceptionally long pectoral 'wings'.

Social Behavior: Highly gregarious, schooling placidly right at the surface. Less prone to panic than dwarf species, but when they do jump, their massive flight muscles produce explosive, loud ballistic jumps that carry them meters away in the wild. Becomes deeply depressed and lethargic if kept in small numbers.

Coloration and Sexual Dimorphism: Brilliant, mirror-like platinum/silver base. The scales are large and heavily outlined, granting an 'armored' appearance. Subtle yellow tinges on the flat back and at the base of the massive pectoral fins. No clear sexual dimorphism besides gravid females being slightly rounder.

Tank Setup: Demands MASSIVE volumes. A proper school requires a minimum 150 cm (5 feet) long tank. A HEAVY, COMPLETELY SEALED LID IS NON-NEGOTIABLE. Additionally, you MUST leave a 4-6 inch (10-15 cm) air gap between the water and the lid/lights; otherwise, these giants will launch into the glass at high speed, snapping their spines instantly. Copious broad-leaf floating plants are required.

Feeding: Extreme macro-insectivore. Has a massive appetite. Feed large freeze-dried insects (crickets, mealworms), jumbo floating pellets, and copious amounts of floating frozen bloodworms and krill chunks. Will starve if forced to dive for food; ignores sinking items completely.

Water Quality: THE PRIMARY CHALLENGE. Almost exclusively wild-caught, suffering heavy losses during shipping. Requires pristine, highly oxygenated water with minimal surface chop. pH 6.0-7.0, soft to medium GH. Temp 24-28°C (75-82°F). Zero tolerance for ammonia, which causes rapid fin corrosion on their 'wings'.

Compatibility: Their sheer size allows them to be the perfect top-dweller for tanks housing jumbo South American peaceful cichlids: adult Discus, Geophagus, Uaru, Severums, and giant Plecos. Do NOT house with aggressive, toothy cichlids (Oscars, Jaguars) or Arowanas that will shred or eat them. Absolute minimum school of 6, ideally 10+.

Reproduction: Essentially unknown in the home aquarium; breeds during massive natural flood cycles.

Risks: 1. LETHAL ACCLIMATION. Over 50% often die from Ich, internal parasites, and shipping stress in the first month unless strictly quarantined. 2. Ballistic suicide against the tank lid. 3. Starvation if water flow pulls food below the surface too quickly.