Green Striped Pencilfish
Green Striped Pencilfish
Green Striped Pencilfish (Nannostomus marilynae) is one of the most unusually colored pencilfish — while most Nannostomus display red or gold stripes, this species has a distinctive greenish to olive-green lateral stripe. Named for Marilyn Weitzman, spouse of ichthyologist Stanley Weitzman.
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. Keep in groups of at least 8. The green stripe is most vivid in well-conditioned fish in soft blackwater with tannins.
A collector find among pencilfish — the unusual green striping distinguishes it from all other commonly available Nannostomus species.
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 | Named for Marilyn Weitzman (wife of ichthyologist Stanley Weitzman). Unusual greenish lateral stripe — distinct from all other Nannostomus species. |
