Barred hemiodus

Geographic Origin and Biotope: Rio Negro and Orinoco basin. Relentless swimmer of the huge open waters of fast-flowing South American river systems, almost never on closed bottoms.

Taxonomy and Morphology: Four-Spotted Hemiodus (Hemiodus quadrimaculatus). Very tapered and hydrodynamic, the "torpedo-suppository" shape betrays a fish made to cut through water. It has the typical "Hemiodus" jaw adapted both for hunting and scraping.

Social Behavior: A rocket in captivity. Perennial swimmer in a loose school; does not tolerate small aquariums. Must be in a group of 6+ to dissipate chronic nervousness: solitary it injures itself by throwing itself against the glass in a panic.

Coloration and Sexual Dimorphism: Gorgeous mirrored silver base framed by a large black spot in the middle of the body and other faded spots. The centerpiece is the tail: the lower lobe is half crossed by a very black oblique ribbon. No visible dimorphism.

Aquarium Setup: Requires the "Track": a tank with at least 150 cm (60 inches) of empty front! Discard intricate furnishings that obstruct their swimming. MANDATORY and weighted LID: their jumps in the water pierce even soft plastic nets.

Diet and Feeding: Micro-predators / Omnivores. They feed in mid-column or on the surface in a frantic manner. They like scattered brine shrimp and bloodworms, mixed with vegetable flakes for their herbivorous streak (they often pick at young vallisneria shoots).

Water Quality: Extremely sensitive (like almost all Hemiodontidae) to pollutants such as nitrites and pH fluctuations; they need titanic filters with high hourly flow rates to simulate the original currents.

Compatibility and Tankmates: Fabulous with Large slow South American Cichlids (Geophagus, Uaru, Severum) and colossal Plecostomus. Their size saves them from large predators, and their mouth is not a danger to any other fish (no Corydoras or Neons).

Aquarium Reproduction: Practically never successfully reported in the domestic environment, due to the need for immense river spaces, strong monsoon rain triggers and advanced age for sexual maturity.

Risks and Diseases: The panic cranial wound (Head-Smash). Just turning on the light suddenly (without a dimmer) is enough for the terrified school to throw itself at tens of km/h against the glass, dying instantly from brain trauma.