What tank size does a Golden Pencilfish need?

A Golden Pencilfish needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.

What water parameters does a Golden Pencilfish need?

Golden Pencilfish does best at 21–27 °C (69.8–80.6 °F), pH 5–8 and a general hardness of 1–15 °dGH.

What group size does a Golden Pencilfish need?

Golden Pencilfish is a social species — keep a group of at least 10 so natural behaviour emerges and stress stays low.

Is the Golden Pencilfish suitable for beginners?

Golden Pencilfish sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.

Species library

Golden Pencilfish

Nannostomus beckfordi

Lebiasinidae

FishDifficulty: ●●●○○Data: well-established

📷 Kaden Slone · CC BY 4.0 · resized · iNaturalist

Golden Pencilfish — Nannostomus beckfordi — 📷 Kaden Slone · CC BY 4.0 · resized · iNaturalist

About

The golden pencilfish is a slender, torpedo-shaped characoid from the coastal and lowland waters of the Guianas and the lower Amazon basin, where it drifts head-up through slow, tannin-stained streams and swampy margins. Hardy and adaptable for a pencilfish yet at its best in soft, acidic blackwater conditions, it is a peaceful mid-to-upper swimmer whose males display harmlessly to one another when kept in a proper group. A large shoal in a shaded, densely planted tank rewards the keeper with rich golden and red flank colours.

Care

Keep a shoal of 10+ in a mature, well-planted tank with gentle flow, soft slightly acidic water and a tight lid. Pair only with small, calm tankmates, never boisterous or large fish.

Diet

Micropredator with a tiny mouth; feed small live and frozen foods daily plus finely ground dry food, as it will not thrive on flake alone.

Tankmate compatibility

Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.

Telling males from females

What works for this species, most reliable first.

Belly depthA hint only · only on well-fed adults, and only as a comparison
For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.

All the methods, with diagrams

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Frequently asked questions

What tank size does a Golden Pencilfish need?: A Golden Pencilfish needs an aquarium of at least 60 litres (15.9 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.
What water parameters does a Golden Pencilfish need?: Golden Pencilfish does best at 21–27 °C (69.8–80.6 °F), pH 5–8 and a general hardness of 1–15 °dGH.
What group size does a Golden Pencilfish need?: Golden Pencilfish is a social species — keep a group of at least 10 so natural behaviour emerges and stress stays low.
Is the Golden Pencilfish suitable for beginners?: Golden Pencilfish sits in the middle of the difficulty scale — manageable for a careful beginner who has done the reading, but it has specific needs worth researching first.

Sources

Water & tank

Temperature21–27°C

Optimal temp.24–26°C

pH5–8

Hardness (GH)1–15°d

Carbonate (KH)0–8°d

Adult size6 cm

Min. volume≥ 60 L

Min. tank length≥ 60 cm

Group size≥ 10

Swimming zoneTop

TemperamentPeaceful

Water typeFreshwater

FlowLow

Lifespan~5 yrs

Try in the calculator