Pencilfish Care Guide: Nannostomus Species for Peaceful Planted Tanks
Slim, elegant and endlessly peaceful, pencilfish belong to the genus Nannostomus and make ideal inhabitants for densely planted aquascapes where delicate beauty matters more than bold flash. This nannostomus pencilfish care guide from Gensou Aquascaping at 5 Everton Park, Singapore, covers the most popular species, their care requirements and the subtle art of bringing out their best colours. In our experience, pencilfish are one of the most underappreciated groups in the hobby, overshadowed by tetras despite offering equal charm with even calmer temperaments.
Popular Species Overview
Nannostomus marginatus (dwarf pencilfish) reaches just 3.5 cm and suits nano tanks from 30 litres up. Nannostomus beckfordi (golden pencilfish) grows to 6 cm and shows striking red and gold horizontal bands. Nannostomus eques (brown pencilfish or rocket pencilfish) swims at an oblique head-up angle, a distinctive behaviour unique to this species. Nannostomus mortenthaleri (coral red pencilfish) is the showstopper, with vivid crimson stripes that rival any marine fish for intensity. Each species has slightly different requirements, but their core care overlaps significantly.
Tank Setup and Aquascaping
Pencilfish originate from slow-moving blackwater streams and tributaries across South America. Replicate this with dense planting, floating plants for shade and gentle filtration. A sponge filter or a canister set to low flow works well. Dark substrate brings out their colours dramatically compared to light sand. Driftwood leaching tannins creates the stained water these fish feel most comfortable in. Tank size depends on species: 30 litres suffices for a small group of N. marginatus, while N. beckfordi schools do best in 80 litres or more.
Water Parameters
Target a temperature of 24-28 degrees Celsius. Singapore’s ambient warmth sits at the upper end of this range, which pencilfish tolerate well. Soft, acidic water with pH 5.5-7.0 and GH 2-8 suits most species. PUB tap water at GH 2-4 is actually ideal after dechlorination, requiring no modification. Add Indian almond leaves or Terminalia catappa extract to lower pH naturally and provide beneficial tannins. Keep ammonia and nitrite at zero and nitrate below 15 ppm, as pencilfish are sensitive to dissolved waste accumulation.
Feeding Pencilfish
Pencilfish have small mouths and require appropriately sized foods. Crush flakes finely or use micro pellets designed for nano fish. Frozen baby brine shrimp, cyclops and daphnia are eagerly accepted and essential for conditioning. Live foods like vinegar eels and microworms trigger the most enthusiastic feeding response. Feed twice daily in small amounts. Pencilfish are not aggressive feeders, so in community tanks, ensure food reaches their preferred mid-water to surface zone before faster tank mates consume everything.
Social Behaviour and Stocking
Keep pencilfish in groups of eight or more. Males of most species establish small territories and display to each other with spread fins and intensified colour, but physical aggression is minimal. N. mortenthaleri males can be mildly territorial, so provide sight breaks with plant clusters. Suitable tank mates include small rasboras, pygmy corydoras, otocinclus and dwarf shrimp. Avoid boisterous species like tiger barbs or larger tetras that outcompete pencilfish at feeding time. The calm demeanour of nannostomus pencilfish makes them perfect companions for shy species.
Night-Time Colour Change
One of the most fascinating traits of pencilfish is their nocturnal colour transformation. At night or in dim lighting, horizontal stripes fade and are replaced by vertical bars or blotchy patterns. This camouflage adaptation can alarm new keepers who think their fish are sick. The normal daytime pattern returns within minutes of lights coming on. This behaviour is entirely healthy and actually serves as a useful indicator: if your pencilfish display their night pattern during the day, they are stressed, and you should check water quality and tank mate compatibility immediately.
Breeding Pencilfish
Breeding is achievable but requires patience. Condition pairs with live and frozen foods for two weeks. Set up a breeding tank with fine-leaved plants like Java moss and dim lighting. Eggs are scattered among vegetation and are not guarded. Remove adults after spawning to prevent egg predation. Eggs hatch in 24-36 hours at 26 degrees Celsius, and fry are extremely tiny, requiring infusoria or paramecium culture for the first week before graduating to vinegar eels. Growth is slow; fry take four to six months to reach recognisable size and colouration.
Why Pencilfish Suit Singapore Planted Tanks
Singapore’s soft, warm tap water matches pencilfish requirements almost perfectly without modification. Their peaceful nature makes them compatible with the Amano-style and Dutch-style planted tanks popular among local aquascapers. Prices range from $3-$5 SGD for common species like N. beckfordi to $8-$15 SGD for the sought-after N. mortenthaleri at specialist shops. A school of pencilfish gliding through a lush carpet of Hemianthus callitrichoides is one of the most refined sights in freshwater fishkeeping.
Related Reading
emilynakatani
Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
