The coral red pencilfish is a tiny, intensely red Peruvian characin with bold black lateral stripes, considered one of the most colorful nano fish available. Dominant males develop spectacular fire-red coloration, especially in a well-planted blackwater aquarium.
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Pencilfish are slender, peaceful nano characins of the genus Nannostomus, named for their pencil-like bodies and lengthwise stripes, prized in planted and blackwater aquariums for their color and gentle temperament.
More pencilfish coming soon.
Habitat & space requirements
From the minimum an animal needs to be kept humanely, up to the ideal setup. Bigger is almost always better — minimums are floors, not targets.
Photo coming soon
Minimum
Shoal nano tank
15 gal / 57 L planted
Nannostomus mortenthaleri is a small (1.5 in) peaceful shoaler. 15-gal planted with soft acidic blackwater, leaf litter, floating plants, and a group of 6+. Easily intimidated — peaceful or species-only.
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Recommended
Planted blackwater shoal
20 gal / 76 L long planted
20-gal long planted blackwater with a shoal of 8–10, dim lighting, and floating plants. Striking red colour develops in stable tannin-stained water.
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Ideal
Amazon biotope shoal
29 gal+ / 110 L+ biotope
Amazon biotope with leaf litter, very soft acidic water, dim light, and a shoal of 12+. Closest to wild Peruvian stream habitat.
Life & growth stages
How this animal changes through its life — each stage often has its own care, diet and space needs.
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Egg
Fish eggs are small, translucent spheres, often laid in clutches on plants, substrate, or in a nest — or carried/brooded by a parent in livebearing and mouth-brooding species. A dark eye spot and the curled embryo become visible inside as development progresses.
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Fry
Newly hatched fry are tiny and semi-transparent, frequently still carrying a yolk sac that fuels them before they feed freely. They lack full fin structure and adult coloration, staying near cover until they can swim and forage on their own.
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Juvenile
Juveniles look like miniature adults but with developing fins and muted or different markings; many species shift pattern and color as they mature. Growth is rapid at this stage given clean water and steady feeding.
Adult
Adults show the species' full size, finnage, and mature coloration, and are sexually mature. Many fish develop sex-specific differences in size, color, or fin shape, which can intensify during breeding.
Habitat & enclosure
A shoal of 8 or more fits a 15-20+ gallon densely planted tank. Recreate soft, acidic Amazonian blackwater: 75-82 F (24-28 C), pH 5.0-6.5, and low hardness. Tannin-stained water from leaf litter and botanicals deepens their color and comfort. Provide gentle flow, dim lighting, and dense planting with open lanes for swimming.
Substrate
Dark fine substrate or sand best displays their red coloration and suits a blackwater theme. A layer of botanicals and leaf litter (catappa/oak leaves) over the substrate both stains the water and provides microfauna for grazing.
Equipment & setup
Gentle filtration (sponge filter ideal), a heater, and dim lighting filtered by floating or dense planting. Add botanicals/leaf litter for tannins. A tight lid is wise as small characins can jump. Stable, soft, acidic water benefits from RO or peat-filtered water in hard-water areas.
Diet
Micropredator with a very small mouth. Feed finely crushed flakes, micro-pellets, and small live or frozen foods: baby brine shrimp, daphnia, cyclops, and microworms. Frequent small feedings of varied, protein-rich foods bring out the best color and breeding condition.
Behavior & temperament
Peaceful but lively, with constant low-level sparring among males that establishes a pecking order and intensifies color — keep several males so aggression is diffused rather than focused on one fish. Best as a shoaling species kept in good numbers. Community-safe with other small, calm nano fish; never a handleable species. Easily intimidated by boisterous or much larger tankmates.
Health
Sensitive to poor water quality and to hard, alkaline water, which dulls color and shortens life. Acclimate slowly to soft, acidic conditions. Susceptible to ich and bacterial issues if stressed or chilled. Stable parameters and a mature, stable tank are key to longevity in this delicate nano species.
Tips, DIY & hacks
Keep multiple males to spread out their harmless sparring and maximize color. Use blackwater botanicals and dim, planted setups for the deepest red. They are egg-scatterers that eat their own eggs; a separate, densely planted or spawning-mop tank improves fry survival. Pair only with peaceful nano tankmates.
