Dwarf Pencilfish
The dwarf pencilfish (Nannostomus marginatus) is among the smallest characins in the hobby, rarely exceeding 3.5 cm. A Lebiasinidae with a slender, near-cylindrical body, it carries three dark longitudinal stripes, the central one edged in red, with carmine flushes on the fins. At night the stripes fade and oblique bars replace them. Described from Maduni Creek in Guyana, it ranges widely through Guyana, Suriname and the middle-to-lower Amazon basin into Peru, Colombia and Brazil. It favours shaded forest streams and blackwater pools carpeted with leaf litter, where the water is very soft, acidic and stained amber with tannins. Gregarious by nature, it needs at least eight companions, ideally ten or more; in a full group the fish grow bolder and rival males posture without harm. A well-planted 60-litre tank with wood, leaf litter and gentle filtration suits a shoal. Its tiny mouth demands small foods — Artemia nauplii, Moina, grindal worm — and its timidity rules out a busy community tank. Breeding is seldom achieved.
About the name : Valid and stable name; the species sits in the family Lebiasinidae (Wikipedia: "belonging to the genus Nannostomus in the characin family Lebiasinidae"). The trade also uses Nannostomus marginatus picturatus for a colour form, treated as a subspecies on the Seriously Fish page title; this entry keeps the binomial Nannostomus marginatus.
Water parameters
| Temperature | 22 – 28 °C |
|---|---|
| pH | 4 – 7 |
| General hardness (GH) | 1 – 10 °dGH |
Tank & stocking
| Minimum tank volume | 60 L |
|---|---|
| Volume budget per individual | 4 L — adds up with tank-mates |
| Minimum group size | 8 individuals (shoaling) |
“Minimum tank volume” is a reasonable floor, not an absolute limit. The per-individual budget is used by the Aqua app to estimate how heavily a tank is stocked.
Frequently asked questions
What size aquarium does Dwarf Pencilfish need?
Provide at least 60 litres for a small group to keep Dwarf Pencilfish in good conditions.
What water parameters does Dwarf Pencilfish need?
A temperature of 22–28 °C, pH 4–7.
Is Dwarf Pencilfish peaceful or aggressive?
Its temperament is peaceful.
What does Dwarf Pencilfish eat?
Its diet: omnivore.
How many Dwarf Pencilfish should be kept together?
It is a social species: keep a group of at least 8.
How big does Dwarf Pencilfish get?
Around 3.5 cm as an adult.
Is Dwarf Pencilfish suitable for beginners?
Care level: intermediate.
Planning a tank with Dwarf Pencilfish?
AquaTender turns these parameters into live advice: it checks whether your tank is big enough, how heavily it's stocked, and whether your fish are compatible — then tracks water tests, photos and maintenance for you.
Fish from the same biotope
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