LARGE Coral Red Pencil Fish (1”+)

Scientific Name: Nannostomus mortenthaleri

Maximum Size & Lifespan:
The Coral Red Pencilfish grows to about 3–4 cm (1.2–1.6 inches) in length. With proper care, it can live 4–6 years in captivity.

Recommended Aquarium Size, Water Changes & Care:
A minimum of 20 gallons (75 liters) is recommended for a small group, as these fish thrive in shoals of at least 8–10 individuals. They require stable, pristine water conditions with soft, slightly acidic water.

• Temperature: 24–28 °C (75–82 °F)

• pH: 5.5–7.0

• Water Changes: Perform 25–30% weekly to maintain water quality and keep stress low.

• Aquascaping: Provide dense planting with live plants such as Java moss, floating vegetation for shade, and open swimming areas. Dark substrate and subdued lighting enhance their vibrant red coloration. Gentle filtration is important, as they do not appreciate strong currents.

Tankmates:
Peaceful, small fish are ideal companions—other calm schooling tetras, rasboras, dwarf corydoras, or small peaceful dwarf cichlids like Apistogramma.

Avoid boisterous or fin-nipping species that could stress them or damage their fins.

Diet:
They are micro-predators, feeding primarily on small invertebrates in nature. In the aquarium, offer a varied diet of:

• High-quality micro-pellets or granules Xtreme Nano Pellets

• Frozen baby brine 

• Occasional crushed flake food for variety

Overview:
The Coral Red Pencilfish is one of the most striking members of the Nannostomus genus, displaying a rich crimson-red body with dark horizontal stripes and a slender, pencil-like profile. Their beauty is best expressed in well-maintained, mature aquariums with a calm environment. Keeping them in groups encourages natural schooling and social displays, reducing shyness and enhancing their coloration.

Natural Environment:
Native to blackwater streams in Peru, particularly around the Nanay River near Iquitos. These waters are slow-moving, shaded by forest canopy, and stained tea-brown from tannins. They are low in minerals and rich in decaying plant matter, with abundant leaf litter and submerged branches.

Breeding:
Coral Red Pencilfish are egg scatterers with no parental care. In breeding setups, use a separate tank with very soft, acidic water (pH 5.5–6.0, temperature 26–28 °C). Provide fine-leaved plants or spawning mops as egg deposition sites. Conditioning with live foods helps trigger spawning. Adults should be removed after spawning to prevent them from eating the eggs. Eggs hatch in 24–36 hours, and fry become free-swimming after 3–4 days, accepting live baby brine shrimp.