Sailfin Tetra

Geographic Origin and Biotope: Amazon River basin (Guyana, Suriname, Brazil). Inhabits small streams in the shade of the dense forest canopy, in flooded areas with exceptional accumulations of dead leaves.

Taxonomy and Morphology: Sailfin Tetra (Crenuchus spilurus). A very rare and archaic characin. Differs from all typical "Tetras" due to its stocky morphology, large mouth and the extreme dimorphism of the males.

Social Behavior: Shy and stationary. Maintains small individual territories. Very static compared to other Characins, it tends to float motionless in the shade or over branches until a morsel passes by.

Coloration and Sexual Dimorphism: Gray/pinkish body with a large black spot framed in gold on the tail ("spilurus"). Adult males develop mastodontic, sail-shaped dorsal and anal fins, spectacular in displays.

Aquarium Setup: Dark aquariums (dim light or thick floating plants). Leaf litter (Indian almond, oak) for tannins and to shield the bottom. Intricate hiding places of branches or small tubes.

Diet and Feeding: Voracious micro-carnivore. Its mouth is disproportionate: it eats large live or frozen prey such as mosquito larvae, bloodworms or adult daphnia. Reluctant towards commercial dry food.

Water Quality: Demands Blackwater environments: very acidic pH (5.5 - 6.0), hardness close to zero and manic cleaning of the substrate. It is very delicate in the face of osmotic shocks.

Compatibility and Tankmates: Fish under 2 cm / 0.8 inches in size (e.g. micro rasboras or young fry) are swallowed whole. Ideal companions are Dwarf Cichlids, peaceful Corydoras or "high" bodied Tetras like Hyphessobrycon.

Aquarium Reproduction: Very rare in captivity, but fascinating: behavior similar to that of Cichlids! The male cleans the roof of a den or leaf, attracts the female there and fiercely guards the brood of eggs until they hatch.

Risks and Diseases: Rapid poisoning in "modern" tanks with neutral pH or high mineral hardness. Death by starvation if fed only with flakes.