Harrison's Pencilfish

Geographic Origin and Biotope: Guyana (Demerara river and other basins). Typical blackwater species: oxbow lakes, swamps and very slow rivers loaded with rotting wood and obscuring tannins.

Taxonomy and Morphology: Harrison's Pencilfish / Blackstripe Pencilfish (Nannostomus harrisoni). The slender "giant" of pencilfish. Very long and filiform (up to 6 cm / 2.3 inches), very thin mouth, but perfectly horizontal posture unlike the eques.

Social Behavior: Compact and stationary schooling fish. Males duel by swimming alongside each other and arching their bodies in harmless visual displays. Must be kept in groups of at least 8-10.

Coloration and Sexual Dimorphism: Features the boldest, widest and most defined black band of the entire Nannostomus genus, crossing the entire body horizontally from eye to tail. The parading male has spectacular vibrant red lower margins.

Aquarium Setup: Tank (min. 80-100 cm / 32-40 inches) furnished with dark roots, many oak leaves on the bottom. Amber water and low light shielded by surface plants are essential to reassure them.

Diet and Feeding: Timid micropredator. Despite its length, it has a microscopic mouth. Must be fed with very fine flakes, daphnia and, primarily, brine shrimp nauplii or finely chopped tubifex.

Water Quality: Unforgiving of neglect. The water must be kept pristine, very soft (GH < 5) and decidedly acidic (pH < 6.5) due to their delicate skins accustomed to peaty rivers.

Compatibility and Tankmates: Absolutely unsuitable for noisy mixed communities. They will NEVER compete for food. Insert together with small timid loricariids (e.g. Farlowella) or small characins (Ember Tetras / Hyphessobrycon amandae).

Aquarium Reproduction: Very complex. They scatter eggs (often a single egg per embrace, rarely and with difficulty) in thick moss. Very prolific in devouring them before they even fall.

Risks and Diseases: Chronic refusal of food. Wild Caught N. harrisoni (the majority on the market) often die of starvation because they do not recognize dry food. It is imperative to slowly accustom them starting only with live or frozen food.