Purple Pencilfish
Purple Pencilfish
Purple Pencilfish (Nannostomus rubrocaudatus) rubrocaudatus means '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) 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 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
| Difficulty | Easy — Moderate |
| Temperament | Peaceful — slow feeder; avoid fast tankmates |
| Typical Adult Size | 1.5 inches (3.8 cm) |
| Min. Group Size | 8 minimum — more females than males |
| Ideal Temp | 73–82°F (23–28°C) |
| Ideal pH | 5.0–7.0 |
| Ideal GH | 0–10 dGH |
| Ideal KH | 0–5 dKH |
| Staple Food | Hikari Micro Pellets (crushed/soaked); Sera Vipan Baby |
| Treat / Supplement | Hikari Frozen or Freeze-Dried Baby Brine Shrimp; Hikari Frozen Daphnia |
| Origin | Amazon and Orinoco basins, South America |
| Notes | Rubrocaudatus = 'red-tailed'. Purple-violet iridescence on flanks combined with red-orange lower body and red tail. Rarely available. |
