Purple Pencilfish – Cuboid Nature Aquarium

Purple Pencilfish

Purple Pencilfish(Nannostomus rubrocaudatus)rubrocaudatusmeans ‘red-tailed’ in Latin — the combination of vivid red-orange lower body, purple to violet iridescent highlights on the flanks, and red caudal fin creates one of the most colorful Nannostomus available.

Feeding & Care Tip:Hikari Micro Pellets(crushed or soaked briefly) andSera Vipan Babymake excellent daily staples. Supplement 2–3× per week withHikari Frozen or Freeze-Dried Baby Brine ShrimpandHikari Frozen Daphnia. Pencilfish are slow, deliberate feeders — avoid fast tankmates that will outcompete them. Feed small amounts 2–3 times daily.

AllNannostomusspecies inhabit the blackwater and clearwater streams, lakes, and flooded forests of the Amazon and Orinoco basins — soft, acidic, tannin-stained water with dense vegetation and leaf litter. A mature blackwater setup with Indian almond leaves, dark substrate, and very soft slightly acidic water produces the most vivid coloration. Males are territorial with each other — keep more females than males and provide visual breaks with dense planting.

The oblique resting posture — head elevated, body angled downward at roughly 45 degrees — is a characteristic behavior of theNannostomusgenus. Schools adopt synchronized oblique positions at rest, which is both fascinating to observe and unmistakable once seen. The angle varies by species — some hold a gentle tilt while others are nearly vertical. The purple-violet iridescence is most vivid in soft acidic water. Keep in groups of 8+.

One of the most colorful pencilfish — the purple iridescence combined with red coloration is exceptional for a small blackwater fish.

Care & Ideal Parameters