Dwarf Pencilfish (Nannostomus Marginatus)

Dwarf Pencilfish (Nannostomus Marginatus) Care Guide

Dwarf Pencilfish (Nannostomus Marginatus) are somewhat a favourite of mine and I think they are very underrated.

Some of the things I like about Dwarf Pencilfish are:

About Dwarf Pencilfish

Dwarf Pencilfish Profile

Origin: Guyana and Suriname and parts of the Amazon basin in Peru, Colombia, and Brazil.

Size: 2 to 2.5cm

Minimum tank size: 10 gallons (38 liters) depending on setup and tank mates.

Tank region: Upper region of the tank.

Water temperature: 72 - 82 °F (22 - 28 °C)

Water conditions: PH between 4 and 7. Soft water with a low TDS is preferred.

Difficulty to keep: Beginner to intermediate level

Dwarf Pencilfish Behaviour And Personality

Dwarf Pencilfish are a peaceful and somewhat shy fish which originate from a wide area including Guyana and Suriname and parts of the Amazon basin in Peru, Colombia, and Brazil.

They usually occupy slow moving almost still water which is typically fairly shallow, heavily planted and contain leaf litter.

They appreciate the company of their own species and usually swim in a loose shoal.

Dwarf Pencilfish Male vs Female


Males are thinner compared to the females.


Females are generally more thickset, rounder and stocky compared to the males.

Dwarf Pencilfish (Nannostomus Marginatus) female on left, male on the right
Dwarf Pencilfish (Nannostomus Marginatus) female on left, male on the right

Feeding Dwarf Pencilfish

In the wild Dwarf Pencilfish mainly feed on insects and other invertebrates at the surface of the water.

In our home aquariums they will accept live or frozen brine shrimp, microworms etc. Dry foods will also usually be accepted. Keep in mind that Dwarf Pencilfish have small mouths so any foods need to be suitably sized.

Slow sinking micro pellets which initially float are a suitable dry food.

Aquarium Setup For Dwarf Pencilfish

As Dwarf Pencilfish can be shy it is important to setup the aquarium so that the fish feel safe and comfortable. I suggest including the following:


They appreciate heavily planted environments. So ensure at least some plants are present in the aquarium, the more the merrier!

Also consider floating plants which will reduce light and proved some added cover.


Adding driftwood which provides areas of cover and breaks in line of sight is also beneficial and mimics their natural habitat.

Leaf litter

Leaf litter is commonly found in the slow moving shallow waters which Dwarf Pencilfish occupy in the wild. Consider adding some leaf litter such as dried almond leaves to your aquarium.


All aquariums require an established filter to maintain water quality for the fish. In the case of Dwarf Pencilfish which inhabit slow moving or even still water it is recommended to have gentle filtration. Air driven sponge filters are a good low cost option.


Depending on your climate and where your aquarium in located a aquarium heater will likely be required. Choose a reputable brand with a wattage to suit the size of your aquarium.

Dwarf Pencilfish Tank Mates

Dwarf Pencilfish are best kept with other small non-aggressive fish such as Tetras or Corydoras Catfish.

Dwarf Pencilfish are also fantastic tank mates for Apsitogramma and other dwarf cichlids since they occupy the upper regions of the tank, leaving the bottom half of the tank available to the dwarf cichlids.


Dwarf Pencilfish (Nannostomus Marginatus) are a underrated fish with unique colors and characteristics.

They occupy the top region of the aquarium and can be a great addition to community tanks.