What size tank does a Coral Red Pencilfish need?

Coral Red Pencilfish needs a minimum of 5 gallons, with 8 gallons recommended. They are middle swimmers. Keep in groups of 8+.

Is Coral Red Pencilfish good for beginners?

Coral Red Pencilfish is rated "advanced" difficulty (3/5). Suitable for intermediate fishkeepers.

What fish are compatible with Coral Red Pencilfish?

Coral Red Pencilfish is peaceful. Compatible tank mates include other peaceful fish with similar water parameters (pH 5-6.5, temp 75-82°F).

Coral Red Pencilfish

Nannostomus mortenthaleri

Family: Characidae • Origin: Various

Coral Red Pencilfish (Nannostomus mortenthaleri) is a peaceful tetra reaching 1.2 inches. Keep in groups of 8+. Minimum tank size: 5 gallons.

Min Tank

5 gal

Max Size

1.2"

Temperature

75-82°F

5-6.5

Lifespan

2 years

School Size

Swim Level

middle

Hardness

5-15 dGH

peacefuladvancedomnivoreschooling

Is Coral Red Pencilfish Right for Your Tank?

Coral Red Pencilfish is a moderate-care fish rated "advanced" (3/5). Suitable for hobbyists with some experience who can maintain stable water parameters. At just 5 gallons minimum, they work well in nano tanks and smaller setups.

With a peaceful temperament, Coral Red Pencilfish makes a great community fish. They coexist well with other non-aggressive species of similar size. This is a schooling species — keep at least 8 together, or they may become stressed and display abnormal behavior. Expected lifespan: 2 years with proper care.

Common Mistakes with Coral Red Pencilfish

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Keeping fewer than 8 together

Coral Red Pencilfish is a schooling species — they need a group of at least 8 to feel secure. Lone or paired individuals become stressed, hide constantly, and may develop health issues or aggression.

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Relying on a heater without a thermometer

Coral Red Pencilfish needs 75–82°F. Heaters malfunction or drift over time — always use a separate thermometer to verify. Temperature swings of even 3–4°F can trigger stress and disease, particularly ich.

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Putting them in a tank under 5 gallons

While 5 gallons is the minimum, nano tanks require more frequent water changes and leave less room for error. A slightly larger tank (8 gal) is much more forgiving.