A tiny, peaceful schooling fish native to the Amazon and Orinoco basins. Known for their torpedo shape, striking horizontal stripes, and fascinating hovering behavior. Their tiny mouths make them one of the few truly dwarf-shrimp-safe fish. They require densely planted tanks with subdued lighting, soft acidic water, and gentle flow to thrive.
Dwarf Pencilfish At a Glance
Dwarf Pencilfish Tank Requirements
Will Dwarf Pencilfish fit in your tank?
Care guides tell you what Dwarf Pencilfish needs, the next question is whether your tank can safely provide it. Test Dwarf Pencilfish against your tank size, maintenance needs, and the fish you already keep before you buy.
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Dwarf Pencilfish Water Parameters
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Dwarf Pencilfish Temperament & Compatibility
Dwarf Pencilfish Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard
The standard form found in the aquarium trade. Must be kept in a shoal of at least 6 to feel secure and display their natural social behaviors and distinct day/night coloration changes.
Same care requirements as the base species
Also known as: Wild Type
Dwarf Pencilfish Care Guide Summary
The Dwarf Pencilfish, scientifically known as Nannostomus marginatus, belongs to the Characins family group. Adults reach a maximum size of approximately 3.5 cm and have a fusiform body shape with a moderate growth rate. Classified as peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a low level of biological waste.
To thrive, the Dwarf Pencilfish requires a freshwater only aquarium with a minimum volume of 40 litres and a tank length of at least 45 cm. Water temperature should be maintained between 22°C and 28°C, with a pH range of 4–7 and a general hardness of 1–10 dGH. A low water flow is preferred.
Due to its specialist needs, the Dwarf Pencilfish is best suited for fishkeepers who can provide a carefully planned setup. The Dwarf Pencilfish is typically available in one standard form.
Dwarf Pencilfish Habitat Setup
When setting up an aquarium for the Dwarf Pencilfish, a low water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include leaf litter or blackwater tannins to replicate their natural soft-water habitat, dense planting to provide cover, break sightlines, and reduce stress, and floating plants to diffuse overhead light and create shaded areas. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Dwarf Pencilfish Compatibility Notes
Classified as peaceful, the Dwarf Pencilfish is a schooling species that feels most secure in a sizeable group, where natural shoaling behaviour reduces stress and brings out their best colours. When choosing tankmates, boisterous or fast-moving tankmates may cause this species undue stress. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Dwarf Pencilfish Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Dwarf Pencilfish.
15 Gallon Standard
20 Gallon High
20 Gallon Long
29 Gallon Standard
30 Gallon Breeder
36 Gallon Bowfront
Show 21 more tank sizes
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Frequently Asked Questions About Dwarf Pencilfish
How big does Dwarf Pencilfish get?
Dwarf Pencilfish (Nannostomus marginatus) typically reaches a maximum adult size of approximately 3.5 cm. They have a fusiform body shape and a moderate growth rate.
What tank size does Dwarf Pencilfish need?
A minimum aquarium volume of 40 litres and a tank length of at least 45 cm are recommended for Dwarf Pencilfish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Dwarf Pencilfish need?
Dwarf Pencilfish thrives in freshwater only conditions with a temperature range of 22–28°C, a pH between 4 and 7, and a general hardness of 1–10 dGH. A low water flow is preferred.
Is Dwarf Pencilfish peaceful or aggressive?
Dwarf Pencilfish is classified as peaceful with an aggression score of 1 out of 10. They are generally well-suited to peaceful community tanks.
How many Dwarf Pencilfish should be kept together?
Dwarf Pencilfish is a schooling species and should be kept in groups of at least 6. Larger groups help distribute aggression and encourage natural schooling behaviour.
Does Dwarf Pencilfish have any special tank requirements?
Yes. Dwarf Pencilfish benefits from plants - densely covered, plants - floating, and leaf litter/blackwater in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Dwarf Pencilfish need a lid on the tank?
Yes. Dwarf Pencilfish is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Top Tank Mates for Dwarf Pencilfish
These fish are strong compatibility matches for Dwarf Pencilfish based on water preferences, temperament, adult size, and tank behavior.
Common Whiptail Catfish
Rineloricaria eigenmanni
Ideal Tank MatesGolden Bristlenose Pleco
Ancistrus sp. L144
Ideal Tank MatesBlack Kuhli Loach
Pangio oblonga
Ideal Tank MatesBee Shrimp
Caridina logemanni
Ideal Tank MatesBanana Loach
Acantopsis choirorhynchos
Ideal Tank MatesWhiptail Catfish
Rineloricaria sp.
Ideal Tank MatesPlants That Suit Dwarf Pencilfish
These plants pair well with Dwarf Pencilfish based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Amazon Frogbit
Limnobium laevigatum
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Carolina Mosquito Fern
Azolla caroliniana
Common Duckweed
Lemna minor
Crystalwort
Riccia fluitans
Fish Similar to Dwarf Pencilfish
Beckford's Pencilfish
Nannostomus beckfordi
A peaceful, slender schooling fish native to the sluggish rivers and swamps of South America. They are famous for the males' harmless but spectacular lateral sparring displays. They require heavily planted aquariums with gentle flow and make excellent tank mates for other peaceful, soft-water species. A tight-fitting lid is essential as they are known to be proficient jumpers.
Dwarf Rasbora
Boraras maculatus
A tiny, peaceful shoaling fish native to the blackwater streams and peat swamps of Southeast Asia. Known for their striking red/orange coloration and distinct dark body spots. They are an excellent choice for heavily planted nano tanks and peaceful dwarf shrimp setups. Because of their minute size, they are easily outcompeted for food and predated upon by larger fish.
MacCulloch's Rainbowfish (Dwarf Rainbowfish)
Melanotaenia maccullochi
A smaller, peaceful species of rainbowfish native to Australia and Papua New Guinea. They feature striking silver/yellow bodies with horizontal red, brown, or orange stripes. Unlike larger Melanotaenia species, their smaller size makes them suitable for medium aquariums. They are highly active schooling fish that require open swimming space and display their best colors in the morning.
Cockatoo Dwarf Cichlid
Apistogramma cacatuoides
A highly popular and vibrant dwarf cichlid native to the Amazon basin. Named for the male's flamboyant, crest-like dorsal fin. They are cave-spawners that require a fine sand substrate (which they sift through their gills) and plenty of hiding spots. While generally peaceful in community tanks, they become fiercely territorial when breeding.
Dwarf Flag Cichlid
Laetacara curviceps
A small, colorful, and surprisingly peaceful dwarf cichlid native to the Amazon Basin. Known for their 'smiling' facial markings and iridescent blue/green flanks. Unlike many of their larger cousins, they are excellent community fish, though they may become mildly territorial when breeding.
Checkerboard Cichlid
Dicrossus filamentosus
A striking, slender South American dwarf cichlid known for its distinct black checkerboard pattern along its flanks. Unlike many cichlids, they are exceptionally peaceful community fish. They are strict blackwater species, requiring very soft, acidic water, sand substrate, and leaf litter to thrive.