Moderate

Dwarf Pencilfish

By The Aquarium Calculators Editorial Team ·

Nannostomus marginatus

Complete Dwarf Pencilfish care guide covering omnivore diet requirements, peaceful temperament, minimum 10 Gallons tank setup, and compatible freshwater tankmates. Difficulty: Moderate.

Dwarf Pencilfish

Quick Answer

Dwarf Pencilfish (Nannostomus marginatus) is a small, elegant fish from South America. It requires a minimum 10 Gallons aquarium with a pH of 5.5 - 7.0 and temperature range of 24-28°C. This omnivore occupies the middle zone and makes an excellent addition to community setups.

Intro

Dwarf Pencilfish (Nannostomus marginatus) is a small, elegant fish from South America. Its slender body is marked with black and gold stripes.

Setup

A 10-gallon or larger tank with dense planting, dark substrate, and dim lighting. They need soft, acidic water and gentle filtration.

Feeding

Omnivorous; accepts micro flakes, baby brine shrimp, daphnia, and crushed pellets. They prefer live/frozen foods.

Compatibility

Peaceful. Keep in schools of 8+. Excellent for nano tanks. Good with other small, peaceful fish: ember tetras, chili rasboras, dwarf shrimp.

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Tank Position
Middle
Water Temp
24-28°C
Adult Size
See profile
Water pH
5.5 - 7.0

Species Characteristics

Adult Size
Lifespan
Growth Rate
moderate
Tank Compatibility
Community compatible
Indoor Aquarium
Yes

Water Parameters

Water Temperature
Humidity
Water pH

Tank Lighting

Tank Lighting
Standard lighting
Light Hours
N/A
Intensity
moderate

Feeding & Diet

Diet Type
Diet: Omnivore
Feeding Schedule
N/A
Live Food Options
N/A

Continue Learning

Recommended Tools

Fish Compatibility Calculator fish compatibility

Health & Disease

Ich (White Spot Disease) common disease • all fish

Related Guides

Understanding pH in Aquariums water parameters • ph

Similar Species

African Leaf Fish Care Guide: Diet & Tank Mates semanticSimilarity Angelfish Care Guide: Tank Size & Diet | The Aquarium Calculators semanticSimilarity Badis Care Guide: Tank Size & Compatibility semanticSimilarity

Frequently Asked Questions

How many Dwarf Pencilfish should be kept together?
Maintain a minimum school of 10 to 15 individuals in a tank of at least 15 gallons (57 liters) with a footprint of 24x12 inches (60x30 cm). Dwarf pencilfish (Nannostomus marginatus) are timid shoalers; groups under 8 cause chronic hiding, stress, and poor coloration. A school of 15+ displays natural angled swimming and social interactions. Maintain a 1 male to 2 female ratio. Provide dense planting (Java moss, Cryptocoryne), floating plants, and dark substrate. Tank height should not exceed 12 inches (30 cm) as they stay in mid-water.
What are the exact water parameters for Dwarf Pencilfish?
Target pH 5.5 - 7.0, General Hardness 2 - 6 dGH, Carbonate Hardness 1 - 4 dKH, Total Dissolved Solids 40 - 120 ppm, Electrical Conductivity 80 - 240 μS/cm, and temperature 73°F - 82°F (23°C - 28°C). They require soft, acidic blackwater parameters with heavy leaf litter. Maintain nitrates below 10 ppm with weekly 20% water changes using RO water. Add Indian almond leaves (1 per 3 gallons) and peat filtration. Use a sponge filter with very low flow. Hardness above 8 dGH causes kidney failure and shortened lifespan. Avoid alkaline substrates.
What is the dietary and medication protocol for Dwarf Pencilfish?
They have very small mouths and are micro-predators requiring 45% protein, 12% fat, 43% plant matter. Feed finely crushed flakes, micro pellets (0.3 mm), live baby brine shrimp, frozen daphnia, and cyclops 3 times daily. They ignore large foods. Offer spirulina powder weekly. Medication alert: Highly sensitive to copper (0.1 mg/L lethal) and formalin. Use malachite green at quarter dose (0.025 mg/L). Praziquantel is safe. Avoid salt (tolerance <2 ppt). Quarantine with methylene blue at half-dose. They are susceptible to velvet; treat with acriflavine.
How to breed Dwarf Pencilfish in a home aquarium?
Condition 15-20 fish with live baby brine shrimp and microworms for 3 weeks. Set up a 10-gallon (38 liter) breeding tank with 4 inches (10 cm) of RO water (pH 6.0, 2 dGH, 78°F/25.5°C), a spawning mop, and java moss. Cover tank sides to create darkness. Simulate dawn with a very dim LED. Spawning occurs in absolute darkness; females scatter 50-100 eggs daily for several days. Remove parents every 2 days. Eggs hatch in 24-36 hours. Fry are 0.06 inches (1.5 mm); require green water (Nannochloropsis) for 5 days, then paramecium, then baby brine shrimp after day 10. Extremely challenging.

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