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Three-lined Pencilfish
Nannostomus trifasciatus
Animalia›Chordata›Actinopterygii›Lebiasinidae
📍 Amazon & Orinoco, South America
Elegant pencilfish with three distinct horizontal stripes and vivid red markings on the fins. Peaceful and slow-moving — ideal for low-flow planted tanks. Best in groups of 8+.
Care Guide
Diet
Three-lined Pencilfish are omnivores requiring small, high-quality foods due to their tiny mouths. Feed a varied diet of micro pellets, crushed flakes, small frozen foods (brine shrimp, daphnia), and occasional live foods once daily in small portions. Supplement with vegetable matter like blanched spinach or algae wafers weekly.
Behavior
These are peaceful, slow-moving fish that spend most time in mid-water levels, often hovering near plants. They are schooling fish that become stressed when kept in groups smaller than 6-8 individuals, displaying more natural behavior and reduced anxiety in larger groups. They are most active during low-light periods and may hide during bright lighting.
Breeding
Breeding in captivity is difficult and rarely achieved in home aquariums. They require very specific conditions including soft, acidic water (pH 5.5-6.5), dense vegetation for egg scattering, and careful separation of fry. Success requires patience, experience, and ideal water parameters that most hobbyists struggle to maintain.
Tank Mates
Similar size, peaceful temperament, and preference for low-flow planted tanks make them ideal companions
Compatible water parameters, peaceful schooling behavior, and similar size create a harmonious community
Shares preference for soft, acidic water and peaceful community setup; similar mid-water swimming zone
Peaceful invertebrates that thrive in planted tanks; pencilfish are too small to threaten them
Essential foreground plant that provides shelter, spawning substrate, and creates the low-flow planted environment they prefer
Dense moss provides hiding places, reduces stress in groups, and creates natural habitat similar to their native environment
Common Diseases
Ich (White Spot Disease)
White spots on body and fins, rapid breathing, lethargy, rubbing against objects
Raise temperature gradually to 28-30°C, perform daily 25% water changes, use aquarium salt (1 tsp per 5 gallons) or commercial ich treatment; treat for 10-14 days
Fin Rot
Frayed or deteriorating fins, discoloration at fin edges, lethargy
Improve water quality with frequent partial water changes, remove any sharp decorations, treat with antibacterial medication if severe; ensure excellent filtration
Neon Tetra Disease
Loss of coloration, curved spine, lethargy, erratic swimming behavior
Unfortunately incurable; isolate affected fish to prevent spread to tank mates, maintain pristine water conditions to slow progression, consider humane euthanasia
Bacterial Infection
Open sores, cloudy eyes, torn fins, loss of appetite
Perform 50% water change immediately, treat with broad-spectrum antibiotic medication, maintain excellent water quality and reduce stocking density
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Quick Facts
- pH
- 5.5–7.0
- diet
- omnivore/micro food
- maxSize
- 1.5 inches
- minTankSize
- 15 gallons
- temperature
- 75–82°F (24–28°C)
Temperature
75–82°F
24–28°C