Golden pencilfish

Geographic Origin and Biotope: Very widespread in Guyana, Suriname and the Brazilian Amazon basin. Lives in flood zones, small secondary streams and swamps, in both clear and dark waters.

Taxonomy and Morphology: Golden Pencilfish (Nannostomus beckfordi). The classic Pencilfish. Hydrodynamic torpedo body, pointed snout and terminal mouth to hunt insects near the surface.

Social Behavior: Dynamic gregariousness (Shoaling). Unlike other timid species, beckfordi males spend 90% of the day dueling each other: they side up, spread their fins and turn black/red in spectacular non-lethal parades.

Coloration and Sexual Dimorphism: Changeable. Golden back, central black stripe. Males lit up by dominance/courtship develop the lower part of a vibrant ruby red and red and black fins. Females remain silvery with a clean stripe.

Aquarium Setup: Minimum 80 cm (32 inches) tank to let them duel. Dense floating vegetation is necessary to shield the lights and bring out the red/black contrast of the males. Branched woods to break the visual range between challengers.

Diet and Feeding: Surface micropredator. They highly appreciate fruit flies (Drosophila) thrown on the water, as well as floating or slow-sinking micro-granules and frozen bloodworms.

Water Quality: The hardiest of the Nannostomus. Adapts to very varied chemistries, forgiving pH tending to neutral and medium hardness, although an acidic environment immensely enhances their colors.

Compatibility and Tankmates: Perfect community fish. Excellent with Dwarf Cichlids (Ramirezi, Apistogramma) as it stays in the middle-upper part of the tank acting as a dither fish without stealing the dens.

Aquarium Reproduction: Simple for a Nannostomus. They scatter sticky eggs among fine-leaved plants (Cabomba or Myriophyllum). In very dense tanks, a few fry survive the ruthless predation of the parents themselves.

Risks and Diseases: Stress from incorrect sex ratio. If too many males and few females are inserted in a small tank, the stress of the constant duel will make the submissive males waste away. Optimal 1 male for every 3 females, or a very large school (15+).