Red Pencil Tetra

Overview

The Red Pencilfish (Nannostomus mortenthaleri) is a premium, deeper-bodied pencilfish with intense red colouration in males. Its distinctive diagonal swimming posture and calm demeanour make it a prized display fish.

Water Parameters

• Temperature: 24–28°C (75–82°F)
• pH: 5.0–6.5 (prefers acidic)
• Hardness: 1–8 dGH (soft water preferred)

Tank Setup

• Minimum tank size: 90 litres for 6+
• Decor: Densely planted with floating cover; dim lighting enhances red colour
• Note: Surface cover is essential — they are mid-to-top dwellers

Diet

• Base: Small flake, micro pellets
• Treats: Small live/frozen foods — daphnia, micro worms, baby brine shrimp
• Note: May be slow to compete for food with faster species

Temperament & Tank Mates

• Temperament: Peaceful, slightly shy; males establish small territories
• Best companions: Small tetras (Ember, Green Neon), rasboras, dwarf shrimp, snails
• Avoid: Boisterous or fast-swimming fish that outcompete them for food

Common Issues

• Colour fades with stress; maintain stable, soft, acidic water
• Can be shy; provide dense planting and floating cover
• Lifespan: 3–5 years