Marbled Headstander

Geographic Origin and Biotope: Endemic to the Amazon and Orinoco river basins in South America. Prefers fluvial areas with weak to moderate current, abundant with submerged marsh vegetation and dense tangles of branches and roots.

Taxonomy and Morphology: Characin belonging to the Anostomidae family. Reaches 14 cm (5.5 inches). Distinguished by its high, laterally compressed body, with a peculiar and conspicuous sail-like dorsal fin that enhances its oblique head-down swimming (Headstander).

Social Behavior: Schooling animal with strong hierarchical tendencies; keeping single specimens makes them fearful or strangely aggressive. It is imperative to form schools of at least 6-8 individuals to disperse the harmless intraspecific skirmishes for dominance.

Coloration and Sexual Dimorphism: Silvery or pale yellow background crossed by vigorous and faded dark gray or brown vertical bands, irregular and "marbled". The lower fins can show amber or orange reflections. Mature females are distinctly thicker and swollen compared to males.

Aquarium Setup: Long tank (at least 120 cm / 4 feet). Set up with sandy bottoms, huge curved woods and smooth rocks. Warning: it will brutally devour almost every live plant; use only very robust epiphytes (Anubias, Microsorum) tenaciously tied to the woods, or synthetic vegetation.

Diet and Feeding: Tireless vegetarian with omnivorous hints. Requires a massive and continuous vegetable intake: blanched lettuce leaves, zucchini, shelled peas, spirulina and wafers for herbivorous fish. Supplement occasionally with bloodworms and krill.

Water Quality: Robust and adaptable, but demands stability. Temperature 23-27°C (73-81°F), pH tendentially neutral or slightly acidic (6.0 - 7.5), medium hardness (GH 4-15). The water must be excellently filtered but without stormy currents unbearable for its swimming.

Compatibility and Tankmates: Relatively peaceful with species of similar size and temperament. Excellent companion for large loricariids, peaceful earth-eating cichlids (Geophagus) and generously sized tetras. Avoid slow, timid tankmates or those with long veil fins (it might nip them).

Aquarium Reproduction: Extremely rare in captivity. Requires huge tanks, very strong thermal and osmotic shocks simulating the rainy season. They are egg scatterers, do not provide parental care and will greedily feast on their own offspring if not removed.

Risks and Diseases: Very robust; however, if deprived of the vegetable component in the diet it will face lethal intestinal obstructions or nutritional deformations. Suffers acute intoxication in case of sudden spikes in ammonia or nitrites.