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Top Fin Aquatics

Rocket Pencil Fish

Rocket Pencil Fish

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Overview of Eques (Diptail) Pencilfish (Nannostomus eques)

Common Names: Eques Pencilfish, Diptail Pencilfish

Scientific Name: Nannostomus eques

Native Location: Amazon and Orinoco Basins

Climate: Tropical

Size: Up to 3.5 cm (1.4 inches)

Temperament: Peaceful

Diet: Carnivore

Breeding: Moderate

Temperature Range: 21° - 27° C (69.8° - 80.6° F)

Preferred pH Range: 6.5 - 7.2

Minimum Aquarium Size: 38 liters (10 gallons)

Potential Tankmates: Peaceful, slow-moving fish

Care Level: Moderate


The Eques or Diptail Pencilfish is a distinctive, loosely schooling fish known for its unique 'head up' posture. This posture helps them blend into their environment to avoid predators. They are popular in the aquarium hobby due to their peaceful nature and adaptability. These fish are typically found in warm, shallow waters in the wild and prefer soft, acidic conditions, although they can adapt to various water parameters in captivity.

Physical Characteristics

Eques Pencilfish have a unique appearance with a 'head up' swimming posture. Their coloration generally includes shades of black, grey, and white, which helps them remain less visible to predators in their natural habitat. They grow to a maximum size of 3.5 cm (1.4 inches).

Behavior and Compatibility

These pencilfish are peaceful and should be kept in groups of five or more to ensure they feel secure. While they are relatively easy to care for, they can be outcompeted for food by larger or faster-moving tankmates. Therefore, it's essential to choose tankmates that are peaceful and not overly aggressive or competitive during feeding times.

Diet and Feeding

Eques Pencilfish are carnivores and thrive on a diet of high-quality live or frozen foods. Suitable foods include:

  • Brine shrimp
  • Bloodworms
  • Daphnia
  • Small insects

They can also adapt to high-quality flake or pellet foods designed for carnivorous fish. Ensure a varied diet to keep them healthy and vibrant.

Tank Setup and Care

  • Tank Size: A minimum of 38 liters (10 gallons) is recommended.
  • Water Conditions: They prefer temperatures between 21° - 27° C (69.8° - 80.6° F) and a pH range of 6.5 - 7.2.
  • Substrate and Decorations: Create a natural habitat with plenty of hiding spots using plants, driftwood, and rocks. They thrive in well-planted tanks with subdued lighting.
  • Water Quality: Regular water changes and maintaining stable water parameters are crucial for their health.


Breeding Eques Pencilfish can be moderately challenging. They require specific conditions to spawn, including:

  • Soft, acidic water
  • Subdued lighting
  • Dense vegetation or spawning mops

Once spawning occurs, the eggs should be protected from adult fish, as they may eat them. Raising the fry can be tricky and requires careful attention to water quality and feeding.

What We Like About This Fish

  • Unique Posture: The distinctive 'head up' swimming posture is fascinating to observe.
  • Peaceful Nature: Suitable for community tanks with other peaceful fish.
  • Adaptability: Can adapt to a range of water conditions, making them versatile for different aquarium setups.


Eques Pencilfish are an excellent choice for aquarists looking to add a unique and peaceful fish to their community tank. Their distinctive behavior and adaptability make them both interesting and relatively easy to care for, provided their tankmates and water conditions are appropriate. Their schooling nature and fascinating posture add a dynamic element to any well-planted aquarium.

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