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Coral Red Pencilfish
Nannostomus mortenthaleri
Animalia›Chordata›Actinopterygii›Lebiasinidae
📍 Rio Nanay, Peru
Arguably the most striking pencilfish, males display vivid coral-red bands separated by deep black stripes. A showstopper in planted nano tanks. Males are mildly territorial but harmless. Prefers soft, acidic water.
Care Guide
Diet
Coral Red Pencilfish require live or frozen micro prey as their primary diet, including small foods like micro bloodworms, daphnia, and copepods. Feed small portions once daily, as their tiny mouths cannot accommodate standard flake food. Supplementing with finely crushed high-quality flakes or specialized micro pellets can help, but live food is essential for optimal coloration and health.
Behavior
These are peaceful, schooling fish that should always be kept in groups of at least 6 to feel secure and display natural behavior. They are mid-water swimmers that spend most of their time in planted areas, moving deliberately through vegetation rather than darting openly. Males display vibrant red coloration and iridescent markings, especially when competing for dominance within the school.
Breeding
Breeding Coral Red Pencilfish in captivity is difficult and rarely achieved in home aquariums. They require pristine, soft, acidic water (pH 5.5-6.5) with dense vegetation for egg scattering, and fry are extremely small and difficult to rear. Success requires patience, specialized conditions, and access to appropriate micro foods for fry.
Tank Mates
Similar size, peaceful temperament, and preference for soft acidic water make them ideal companions
Peaceful algae eater that thrives in the same soft, acidic conditions without competing for micro prey
Compatible water parameters; shrimp are small enough not to threaten pencilfish but may compete for some foods
Foreground plant that provides shelter and natural habitat structure pencilfish prefer
Low-light plant that creates the dense vegetation pencilfish need for security and natural behavior
Peaceful dwarf cichlid with similar water needs, but larger size means careful monitoring to prevent predation on pencilfish
Common Diseases
Ich (Ichthyophthirius multifiliis)
White spots on body and fins, rapid breathing, flashing against surfaces, lethargy
Gradually raise temperature to 28-30°C, perform frequent water changes, use aquarium salt or ich medication; maintain excellent water quality
Fin Rot
Frayed or disintegrating fins, darkening at fin edges, lethargy
Perform large water changes, improve water quality, use antibacterial medication if severe; ensure soft, acidic water parameters are maintained
Malnutrition/Color Loss
Fading red coloration, lethargy, stunted growth, loss of iridescent markings
Increase frequency and variety of live micro prey; ensure diet includes quality frozen foods like micro bloodworms and daphnia
Bacterial Infection
Open sores, cloudy eyes, torn fins, behavioral changes
Perform daily water changes, maintain pristine water conditions, use broad-spectrum antibacterial treatment if necessary
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Quick Facts
- diet
- Micro omnivore – micro pellets, baby brine shrimp, daphnia
- lifespan
- 3–5 years
- max size
- 3 cm (1.2 in)
- tank size
- 10 gallons minimum
- school size
- 8+
- temperament
- Peaceful, mildly territorial males
Water it likes
- ph
- 4.5–6.5
- ammonia
- 0 ppm
- nitrate
- <10 ppm
- hardness
- 1–5 dGH
- temperature
- 75–82°F (24–28°C)