Pencilfish Care Guide: Slender Elegance for Planted Tanks
Few freshwater fish carry themselves with the quiet grace of the pencilfish. Named for their slender, torpedo-shaped bodies, these miniature schooling fish from the Nannostomus genus have steadily gained fans among planted tank enthusiasts in Singapore — and for good reason. Their subdued elegance, peaceful temperament and compatibility with warm, soft water make them a natural fit for our tropical setups.
In this pencilfish care guide, we cover the most popular species, ideal tank conditions, feeding, breeding and everything you need to keep these gentle schoolers thriving in a Singapore aquarium.
Table of Contents
What Are Pencilfish?
Pencilfish belong to the genus Nannostomus, a group of small characins native to the blackwater streams and flooded forests of South America. The name Nannostomus translates roughly to “small mouth,” reflecting their tiny, upturned feeding apparatus.
What sets pencilfish apart from other nano fish is their distinctive body shape — elongated and cylindrical, like a sharpened pencil — and the fascinating habit some species have of resting at an oblique, head-up angle. This tilted posture is perfectly normal and adds to their unique charm.
Most species stay between 2.5 cm and 5 cm, making them excellent residents for planted nano and medium-sized aquariums. They hail from soft, acidic waters with gentle flow, conditions that are straightforward to replicate in Singapore.
Popular Pencilfish Species
Several Nannostomus species turn up regularly in Singapore fish shops. Here are the four you are most likely to encounter:
| Species | Common Name | Adult Size | Key Feature |
|---|---|---|---|
| N. beckfordi | Golden Pencilfish | 3.5–4 cm | Hardy, golden-red lateral stripe; best beginner species |
| N. eques | Brown Pencilfish / Diptail | 4–5 cm | Iconic head-up resting posture; hovers at 45 degrees |
| N. marginatus | Dwarf Pencilfish | 2.5–3 cm | Tiny size, bold black and red stripes; ideal for nano tanks |
| N. mortenthaleri | Coral Red Pencilfish | 3–3.5 cm | Vivid red and black bands; the showpiece of the genus |
Beckford’s Pencilfish (N. beckfordi)
The most commonly available and arguably the hardiest pencilfish. Its golden body with a dark lateral band and red-orange fin accents makes it attractive without being demanding. A solid starting point for anyone new to the genus.
Brown Pencilfish (N. eques)
This species is famous for hovering at roughly 45 degrees, head pointed upward — an unusual and captivating sight in a planted tank. It occupies the upper water column more than other pencilfish, making it a good complement to bottom-dwelling species.
Dwarf Pencilfish (N. marginatus)
At barely 3 cm, the dwarf pencilfish is one of the smallest species in the hobby. Its neat red, black and cream horizontal stripes are surprisingly bold for such a diminutive fish. Perfect for nano setups of 20 litres or more.
Coral Red Pencilfish (N. mortenthaleri)
The undisputed gem of the pencilfish world. Males in breeding condition display intense crimson red bands separated by jet black — a colour combination that looks stunning against lush green plants. They command a higher price, but the visual impact is well worth it.
Tank Setup and Water Parameters
Pencilfish come from slow-moving blackwater habitats, so replicating a calm, softly lit environment is the key to bringing out their best colours and natural behaviour.
| Parameter | Ideal Range | Notes |
|---|---|---|
| Temperature | 24–30 °C | Singapore’s ambient 28–32 °C is fine; use a fan if consistently above 30 °C |
| pH | 5.5–7.0 | Slightly acidic preferred; driftwood and botanicals help |
| GH | 2–10 dGH | Soft water ideal; Singapore tap water may need dilution with RO |
| KH | 1–5 dKH | Low buffering suits them |
| Tank Size | 40 litres+ | Dwarf species can work in 20 litres; larger groups need 60+ litres |
Filtration and Flow
Keep flow gentle. A sponge filter or a hang-on-back filter with the output baffled works well. Pencilfish are not strong swimmers and will stress in high-current setups. In Singapore, always treat tap water with a conditioner that neutralises chloramine — PUB’s disinfection method — before adding it to the tank.
Aquascaping for Pencilfish
Dense planting is essential. Pencilfish feel most secure among fine-leaved plants such as Rotala, Myriophyllum and Java moss. Floating plants like Salvinia or Amazon frogbit dim the lighting and encourage pencilfish to display their boldest colours. Driftwood and leaf litter complete the blackwater aesthetic and release beneficial tannins.
If you need help designing a planted tank around pencilfish, our custom aquarium service can create a setup tailored to these fish.
Feeding Pencilfish
Pencilfish have small mouths, so food size matters. Crush standard flakes or use micro pellets. A varied diet keeps them healthy and colourful:
- Micro pellets — a convenient staple; choose slow-sinking varieties
- Crushed flake food — acceptable but messy; feed sparingly
- Baby brine shrimp — live or frozen; excellent for conditioning and colour
- Daphnia — frozen or cultured; a natural food source
- Micro worms and vinegar eels — ideal live foods for tiny mouths
- Grindal worms — higher fat content; offer once or twice a week
Feed small amounts twice daily. Pencilfish are not aggressive feeders, so ensure food reaches them before tankmates gobble everything. You can find quality micro foods and frozen feeds at our online shop.
Behaviour and Schooling
Pencilfish are peaceful schooling fish that should be kept in groups of eight or more. Smaller groups result in skittish, pale fish that hide constantly. In a proper school, they cruise through the mid-water column in loose formation, occasionally sparring gently — males flare at each other with fins spread, a display that causes no harm.
Some species, particularly N. eques, hover almost motionless in the upper third of the tank, angled head-up. Others, like N. marginatus, stay in the mid-level among plant stems. Understanding each species’ preferred zone helps you plan a community tank with minimal territorial overlap.
Night Colour Pattern Change
One of the most fascinating features of pencilfish is their nocturnal colour transformation. When the lights go off, their daytime stripes and bands fade and are replaced by a completely different pattern — typically a series of dark blotches or spots on a pale body.
This camouflage mechanism helps protect them from predators in the wild during their vulnerable sleeping hours. If you switch the aquarium light on suddenly at night, you will see this alternate pattern before it fades back to normal within minutes. It is a harmless, natural phenomenon and quite remarkable to witness.
Tank Mates
Pencilfish are gentle and non-confrontational, so choose tankmates of similar temperament:
- Good choices: Corydoras catfish, small rasboras, otocinclus, small tetras, dwarf shrimp (adults), snails
- Avoid: Aggressive or boisterous fish such as tiger barbs, large cichlids, or anything that will outcompete them for food
In HDB and condo setups where space is limited, a 60 cm planted tank with pencilfish and Corydoras makes an elegant, low-drama community.
Breeding Pencilfish
Breeding pencilfish is achievable but requires some preparation:
- Condition breeders with live and frozen foods for two weeks.
- Set up a separate breeding tank (10–20 litres) with soft, acidic water (pH 5.5–6.5, GH below 4).
- Add fine-leaved plants or spawning mops — eggs are scattered among vegetation.
- Introduce a conditioned pair or trio (one male to two females).
- Remove adults after spawning — pencilfish are egg scatterers and will eat their own eggs.
- Eggs hatch in 24–48 hours. Feed fry infusoria, then newly hatched brine shrimp after a few days.
Males are typically slimmer with more intense colour. Females are rounder when gravid. Breeding is easier with blackwater conditions — Indian almond leaves or peat extract help achieve the right chemistry.
Frequently Asked Questions
Are pencilfish suitable for beginners?
Yes, particularly N. beckfordi, which is hardy and forgiving of minor parameter fluctuations. The key requirements are soft water, gentle flow and a school of at least eight. Beginners who can meet these conditions will find pencilfish rewarding to keep.
Can I keep pencilfish in a nano tank?
Dwarf pencilfish (N. marginatus) can thrive in tanks as small as 20 litres. Larger species like N. eques need at least 40–60 litres to school comfortably. Regardless of tank size, dense planting and low flow are non-negotiable.
Why do my pencilfish look pale?
Pale colouration usually indicates stress. Common causes include insufficient group size (keep eight or more), excessive light without shaded areas, aggressive tankmates, or water parameters outside their preferred range. Adding floating plants and tannin-staining botanicals often produces a rapid improvement.
Do pencilfish eat algae?
No. Pencilfish are micro-predators that feed on tiny invertebrates and insects in the wild. They will not help with algae control. For planted tanks that need an algae crew, consider pairing pencilfish with otocinclus or nerite snails.
Bring Pencilfish Elegance to Your Home
Pencilfish offer something rare in the aquarium hobby: genuine subtlety. In a world of flashy, hyperactive fish, their calm schooling, fascinating night-time colour shift and slender beauty stand apart. For Singapore aquarists with planted tanks, the warm ambient temperatures and availability of quality live foods make keeping pencilfish straightforward and satisfying.
Whether you are drawn to the beginner-friendly beckfordi or the showstopping coral red, pencilfish deserve a place on every planted tank shortlist. If you would like advice on species selection or a planted setup designed around these elegant fish, get in touch with us — our team at 5 Everton Park has over 20 years of aquascaping experience to draw on.
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