Dwarf Pencilfish

Nannostomus marginatus is among the tiniest pencilfish, rarely exceeding 3 cm, and is a favourite for nano planted aquariums. Its body is pale cream to yellowish, traversed by a bold black lateral stripe edged above with a vivid red line. Males are notably slimmer and more intensely coloured than females, especially in soft acidic water.

This species is entirely peaceful and can be housed with other small, gentle fish such as ember tetras, chili rasboras, and small shrimp. It thrives in dimly lit tanks with dense vegetation, floating plants to filter light, and a dark substrate that helps it feel secure and display its best colours.

Small foods are essential: baby brine shrimp, micro-worms, vinegar eels, and high-quality micro-pellets. Its tiny mouth means standard flake should be crushed finely. Stable water chemistry — soft and acidic — is critical for health and breeding.

Water: 23–28°C, pH 5.0–7.0, soft (GH 1–8, KH 0–4); blackwater conditions ideal. Tank: 40 L minimum; planted nano with floating cover, dark substrate, leaf litter encouraged. Feeding: Micro-pellets, crushed flake, baby brine shrimp, micro-worms, and vinegar eels. Breeding: Egg-scatterer among fine-leaved plants; fry tiny — start on infusoria and rotifers. Compatibility: Ideal with ember tetras, chili rasboras, small shrimp, and peaceful nano species only.