Coral Red Pencilfish

Coral Red Pencilfish (Nannostomus mortenthaleri) is arguably the most spectacular pencilfish available — males develop an extraordinary coral-red to deep red coloration covering the entire lower body and fins, with the upper body silvery-white. Listed as IUCN Near Threatened and endemic to the Río Nanay drainage near Iquitos in Peru.

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

All Nannostomus species 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 the Nannostomus genus. 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 coral-red coloration is most vivid in soft, acidic water with tannins. A mature blackwater setup is important. Keep in groups of 8+ with more females than males.

One of the most beautiful nano fish available — the coral-red male coloration is extraordinary. The restricted range and Near Threatened status make captive breeding a meaningful contribution.

Care & Ideal Parameters