Barred pencilfish
Nannostomus espei
A rare, sought-after pencilfish from the Mazaruni River system in Guyana, from blackwater habitats with extreme pH (4.0–6.5). The body is crossed by alternating dark vertical bars giving it a unique pattern in the genus. Extremely shy: needs schools of at least 8–12 in mature, quiet tanks. Species-only tank strongly recommended. Requires live or frozen food daily — dry food alone is insufficient. Never add to uncycled tanks.
Water Temperature
24 - 28 °C
pH Value
5.5 - 7
Water type
Freshwater
Tank level
Middle
Adult size
3.5 cm
Minimum tank volume
>= 40 L
Minimum group
>= 8
GH
1 - 8 dGH
KH
1 - 4 dKH
TDS
25 - 160 ppm
Conductivity
39 - 250 uS/cm
Species description
Geographical Origin and Habitat: Mazaruni River Basin (Guyana). Inhabits shaded forest streams (Igarapés), where slow, crystal-clear waters flow over beds of sand and fallen branches.
Taxonomy and Morphology: Espe's Pencilfish / Barred Pencilfish (Nannostomus espei). Among the rarest pencilfish on the market. Tiny torpedo morphology, almost completely lacks the long central black stripe, typical of the genus.
Social Behavior: Peaceful school (Shoaling). Very stationary in mid-water. Unlike beckfordi, males exhibit few skirmishes, spending time in tight inclined or horizontal formations inspecting leaves.
Coloration and Sexual Dimorphism: Unique "comma" pattern: instead of the horizontal line, it has 5 large oblique black spots/commas ("barred") arranged on the light flanks with gold reflections. This pattern serves to camouflage among fine debris. Males are slenderer and have dark tips on the anal and dorsal fins.
Care, breeding and tankmates
Aquarium Setup: Biotope for specialists. Minimum tank 60 cm (24 inches). Very weak sponge filter, lots of Cryptocoryne, Echinodorus or Moss. Dim light is mandatory to make them come out in the open.
Diet and Feeding: Mid-water micropredator. Requires extra-small granules (less than 0.5 mm), newly hatched live brine shrimp, and frozen Cyclops. They will refuse bites that are too hard or large pieces.
Water Quality: Requires pristine and stable waters. Ph 6.0 and low GH. Although it comes from clear waters (Clearwater), the addition of peat to gently lower the Ph is highly recommended (simulating the acidity of the tropical forest).
Compatibility and Cohabitation: "Species Tank" jewel. Can be joined (at most) with Corydoras panda, Otocinclus, Paracheirodon innesi (Neon tetras). They will desperately flee from hyperkinetic fish like Danios.
Aquarium Breeding: Challenge for experts. They lay few eggs in dense vegetation. Parents are not famous devourers of their eggs (like other Nannostomus), but the fry are so minute as to require weeks of paramecia.
Risks and Diseases: Water stress decay. The Espei has little tolerance for powerful filters. If forced to swim against the current to maintain position (which they hate), they will consume all their energy, rapidly falling ill with fungal infections.
Geographic origin and distribution
Mazaruni River Basin (Guyana). Inhabits shaded forest streams (Igarapés), where slow, crystal-clear waters flow over beds of sand and fallen branches.
Origin
Tropical oceans and reefsAmazon, Orinoco, and Guianas
Fish profile
- Temperament
- Peaceful
- They are remarkably peaceful, somewhat shy, and easily stressed by boisterous activity. Providing ample plant cover gives them the confidence to swim openly. Once settled, their distinctive comma-shaped markings and calm demeanor are beautiful.
- Diet
- Carnivore
- They are micro-predators requiring appropriately sized, high-quality foods. Crushed premium flakes, micro-pellets, and baby brine shrimp are excellent choices. Live cultures like microworms are highly beneficial for their overall vitality.
- Life expectancy
- 3-5 years
- Adult size
- 3.5 cm
- Sex ratio
- School
- Keeping a mixed-sex group of at least six individuals is recommended. Males may engage in harmless lateral displays to establish a mild hierarchy. A larger group helps them feel secure and displays their natural schooling behaviors.
- Feeding frequency
- Twice daily
- Feed them very small amounts two to three times a day. Their tiny mouths and digestive systems cannot process large, infrequent meals. Careful feeding ensures all individuals in the school receive adequate nutrition.
- Bioload
- Low
- Espe's Pencilfish produces a very low bioload, similar to other micro fish. They are well-suited for smaller, biologically established aquariums with pristine conditions. A gentle filtration system easily handles their minimal waste production.
- Flow
- Strong
- They prefer calm, slow-moving waters characteristic of their natural habitats. Strong currents from powerheads or large filters will quickly tire them out. A sponge filter provides the perfect balance of gentle flow and filtration.
- Jump risk
- No
- Reproduction
- Oviparous
- Breeding Espe's Pencilfish is a rare achievement requiring highly specific water parameters. They are egg scatterers that lay their eggs among fine-leaved aquatic mosses. The parents will consume the eggs, so immediate separation is necessary.
- Compatibility & tankmates
- Community
- They are highly peaceful and do well in communities of small, non-aggressive fish. Ideal tank mates include dwarf rasboras, small peaceful tetras, and shrimp. Larger fish will easily intimidate them and outcompete them for food.
- Tank level
- Middle
- They primarily inhabit the middle to upper levels of the aquarium. They appreciate tanks with tall background plants that reach the surface. They rarely descend to the bottom substrate during normal daylight hours.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
FishBase v25.04Data synced on: 06/15/2026
- Trophic level
- 3.3 ± 0.4 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.5
- Bayesian Length-Weight
- a = 0.00646, b = 3.13
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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