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No federal permit to keepThreestripe pencilfish
Nannostomus trifasciatus
Fishes › Tetras, piranhas and pacus (Characiformes) › Lebiasinidae (Pencilfish and splash tetras)
Nannostomus trifasciatus (from the Greek nanos, meaning "small"; the Latin stomus, relating to the mouth; and the Latin trifasciatus, meaning "three bands"), commonly known as the three-lined or three-stripe pencilfish, is a freshwater species of…
Care at a glance
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 1.4 in / 3.6 cm).
- Water: Freshwater.
- Temperature: 75–82°F (range recorded for this species).
- pH: 5.5–7.
- Hardness: 0–4 dGH.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Diet: A predator: feed meaty foods sized to its mouth (frozen fish, shrimp, worms); it will eat tankmates that fit in its mouth. FishBase classes it as a carnivore.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 30 × 12 in (roughly 18 US gallons); space needed is rated “modest tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 72–82 °F, pH 4–7.5, 1–12 dGH.
- Behaviour: temperament peaceful; a shoaling fish best kept in a group of six or more; suited to a community tank.
- Difficulty: Easy (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “Should ideally be kept in a heavily-planted set-up, preferably with a dark substrate.”
- Diet: “A micropredator feeding on tiny invertebrates and other zooplankton in nature.”
- Tankmates: “Relatively peaceful and will not compete well with very boisterous or much larger tankmates.”
- Breeding: “An egg-scattering free spawner exhibiting no parental care.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Pencilfish and splash tetras
Applies to most species in this group. Habitat: Common pencilfish and splash tetras inhabit vegetated South American streams and tributaries, with Copella also entering flooded forest. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- N. beckfordi needs a base of at least 18 × 12 inches; C. arnoldi needs at least 36 × 12 inches for long-term care.
- Use dense planting, floating plants, branches and leaf litter for shade and broken sight lines.
- Use gentle filtration for pencilfish; provide well-oxygenated water with slight surface agitation for splash tetras.
- For breeding C. arnoldi provide about 4 inches between water and cover, plus overhanging spawning surfaces.
- Use a biologically mature aquarium; splash tetras are sensitive to chemistry swings.
Climate & lighting
| Water | 69.8–80.6°F |
Diet
- Dry foods small enough for their mouths.
- Daily small live or frozen Artemia nauplii, Moina or grindal worms.
- Small gut-loaded fruit flies or crickets for C. arnoldi.
Social life
- Keep N. beckfordi in groups of 10 or more and C. arnoldi in mixed-sex groups of 8–10; choose peaceful small companions. Male pencilfish spar, so provide visual barriers.
Health watch
- Water-quality stress in immature aquaria.
- Nutritional deficiencies from unsuitable food sizes or limited diets.
- Freshwater white spot and other skin/gill parasites.
Understanding the animal
About this animal
About this animal
They are popular in the aquarium trade due to their small size, beautiful color pattern, and relative hardiness.
Quoted from the Wikipedia article “Nannostomus trifasciatus” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater. Uses both the bottom and open water. Feeds on worms, crustaceans and insects. |
| Water it lives in | Freshwater, 75–82 °F (24–28 °C), pH 5.5–7, hardness 4 dH. |
| Climate | Tropical climate. |
| Wild diet | Hunting macrofauna (predator). |
| Behavior to plan for | Breeding: open water/substratum egg scatterers. |
What this means for care
- Keep water within its wild range, 75–82 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 90°F (up to 93°F in the hottest sampled areas) |
| Cool-season lows | about 70°F (down to 65°F in the coldest sampled areas) |
| Average temperature | 78–81°F across sampled records |
| Relative humidity | 80–84% on average (driest month about 77%) |
| Rainfall | about 2392 mm a year |
Measured at 228 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | Nannostomus trifasciatus (from the Greek nanos, meaning "small"; the Latin stomus, relating to the mouth; and the Latin trifasciatus, meaning "three bands"), commonly known as the three-lined or three-stripe pencilfish, is a freshwater species of fish belonging to the characin family Lebiasinidae. They are popular in the aquarium trade due to their small size, beautiful color pattern, and relative hardiness. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Social life and communication | Little is known about communication in N. trifasciatus. — Animal Diversity Web |
| Wild diet | N. trifasciatus spends much of its time near the water surface, where it feeds primarily on insects. — Animal Diversity Web |
| Behavior | This species is active during the day, resting at night in the upper layers of the water. — Animal Diversity Web |
| Reproduction | N. trifasciatus spawns during the daytime among plant leaves. — Animal Diversity Web |
| Appearance and size | The three-lined pencilfish is a small fish, with adults not reaching more than 6 cm in length. — Animal Diversity Web |
| Biology | Feeds on worms, crustaceans and insects. — FishBase |
| History and naming | Steindachner first described the species in 1876, making it one of the first four species in the genus to be described. As a result of the broad distribution of N. trifasciatus, the species is polymorphic and, over the years, some of these color morphs have been erroneously described as separate species. Poecilobrycon erythrurus and Poecilobrycon vittatus, two such examples, are now known to be junior synonyms. — Wikipedia (community-edited) |
| Conservation | N. trifasciatus is fairly common throughout its home range, and because it is bred easily in captivity for the aquarium trade, it is unlikely that this species will face extinction in the near future (Torres et al., 2002; Goulding et al., 1988; Sterba, 1963; McInerny, 1958; Innes, 1956). — Animal Diversity Web |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Typical adult weight
Average adult body mass in each database (FishBase gives the maximum recorded weight).
Adult length
Maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 30 × 12 in (about 18 US gallons).
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Nannostomus beckfordi — Seriously Fish Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Copella arnoldi — Seriously Fish Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Disorders and Diseases of Fish — Merck Veterinary Manual Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Parasitic Diseases of Fish — Merck Veterinary Manual Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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