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Species profile

Dwarf Pencilfish

Nannostomus marginatus

Common names: Dwarf Pencilfish

Recognized speciesPencilfish
Dwarf Pencilfish (Nannostomus marginatus)

Adult size

Up to 2.5 cm

Typical adult length 2–2.5 cm.

Up to 2.5 cm

Countries of origin

  • See all stock from Brazil
  • See all stock from Colombia
  • See all stock from Guyana
  • See all stock from Peru
  • See all stock from Suriname

Good fit for your tank?

Good fit for

  • A soft-water nano aquarium
  • A tank with very small, calm fish
  • A companion for dwarf cichlids

Think carefully if

  • Your water is hard or alkaline
  • Your tankmates are large or active
  • You can only keep a few fish

A tiny, striped pencilfish from South America, about 2.5 cm long. It is timid and gentle, and it suits soft-water nano aquariums with small, calm tankmates.

Appearance and Identification

A tiny, stocky pencilfish with dark horizontal bands, a gold line, and red spots in the fins.

Small size and bold horizontal stripes are the main features. Several geographic forms exist.

Males are slimmer than females.

Tank Requirements

Suggested filter
About 80–120 litres an hour
Suggested heater
About 50–75 W for this tank
Minimum tank volume
40 litres
Minimum tank length
45 cm
Minimum group size
10
Recommended group size
10
Activity level
Low
Flow preference
Very low
Planting preference
Heavily planted
Hiding places
Yes
Lid recommended
Yes
Jumping risk
Low

Use dense planting, leaf litter, and dim light with a gentle sponge filter. Guard filter intakes because this fish is very small.

Behaviour and Tankmates

Peaceful but timid, staying among plants until it feels secure.

Keep at least 10 together. Fish are gregarious and show more natural behaviour in groups.

Not strongly territorial.

Suits smaller peaceful characins and catfish, and works as a shoaling companion for dwarf cichlids. Avoid large or boisterous fish.

Check tankmates for this species

Water Parameters

Temperature
22–28 °C
pH
4–7
GH
1–10
Stability importance
Important

Soft, acidic water suits this fish best. Change water gently.

Parameter caveat
Small tanks change quickly, so keep up with gentle water changes and acclimate slowly.

Feeding

Diet types
Insectivore, Omnivore
Feeding frequency
Once or twice daily
Preferred foods
  • Fine micro granules or crushed flakeUse a particle size the fish can swallow whole, and feed only what is eaten within a couple of minutes.
  • Frozen or live daphnia and cyclopsSmall crustaceans add variety and help bring adults into breeding condition.
  • Frozen or newly hatched brine shrimpA good small meat food a few times a week rather than the only food.

A micropredator that needs very small food.

Use the smallest foods available, and make sure faster fish do not take them first.

Breeding

Breeding type
Egg Scatterer
Breeding difficulty
Difficult
Brood or egg count
Not well documented
Parental care
None
Baby foods
  • Infusoria or parameciumNeeded for the first days after fry become free-swimming, because the fry are very small.
  • Fine powdered fry foodUse sparingly as a supplement, and siphon out anything left uneaten.
  • Newly hatched brine shrimpIntroduce once the fry are large enough to swallow it, usually after several days.
  • MicrowormsA useful next step for fry that are still too small for brine shrimp.

Rarely achieved in aquariums. Spawning is more reliable with adults conditioned separately and with spawning mops. Feed the fry on infusoria or fine dry food.

Habitat and Origin

Geographic origin
Amazon Basin, Brazil, Colombia, Guyana, Peru, South America, Suriname
Natural habitat
Blackwater, Slow River, Vegetated Shoreline
Aquarium contexts
Breeding Aquarium, Nano Aquarium, Planted Aquarium
Audience level
Intermediate

Classification

Profile type
Recognized species
Genus
Nannostomus
Family
Lebiasinidae
Species group
Fish, Pencilfish

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