At a glance the quick version
Looks how to spot one
Short, stocky scaled characin
A small, compact pencilfish with three bold dark stripes. Males glow a vivid red from the snout to the tail, with a white mark and red tip at the front of the dorsal fin. Females are plumper and lack the red body colour. At night both sexes turn much paler while the stripes stay visible.13
Personality what they are like
Peaceful toward other kinds of fish but shy because of its small size, so it suits a quiet species-focused tank or a few calm companions such as Apistogramma. Males are more spirited than most pencilfish and hold small territories, sparring with each other.13
Daily activity how busy a day looks
Active among plants in the middle and lower water, with males patrolling and displaying.1
Grooming and care the hands-on bits
Needs very soft, acidic water. Suggested ranges: 24-28 C, pH 4.0-7.0, hardness 1-5 dGH. Keep water clean and stable with gentle filtration.1
Home where they are happiest
Tank of at least 90 cm length (about 81 litres) with dense planting, wood and leaf litter that break up sightlines so each male has his own space.13
Food basics what goes in the bowl
A micropredator of tiny invertebrates and zooplankton. Offer small dried foods along with live or frozen brine shrimp nauplii, moina and grindal worms.1
Company who they like around
Best in a group of 10 or more, with plenty of cover so the males can share space comfortably.1
The story where it all began
First described in 2001 as a subspecies of the dwarf pencilfish, it was raised to full species status in 2003. It is named after Martin Mortenthaler, an Austrian fish exporter who collected the first specimens.12
Fun facts for the dinner table
- 1
It was named after Martin Mortenthaler, the exporter who discovered it.2
- 2
It is known from only one small part of Peru, near the city of Iquitos.1
- 3
It was first treated as a subspecies of the dwarf pencilfish before being recognised as its own species in 2003.1
- 4
It belongs to the stubby-bodied pencilfish group rather than the long, slim ones.3
Recognised by the official bits
- IUCN Red List
- Critically Endangered (assessed April 2014)2
- FishBase
- Described by Paepke & Arendt in 20012
The care rhythm a typical week and year
A typical home-care rhythm for a Coral Red Pencilfish. A starting point, not a vet's advice.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
Owner questions the things everyone asks
How often should I feed my Coral Red Pencilfish?
Feed small amounts once or twice a day, as Furry Diary's starting plan suggests. This matches their natural micropredator diet and keeps the water clean.1 Pet Wiki plan
What does a Coral Red Pencilfish eat, and what should it never eat?
They eat tiny invertebrates and zooplankton, so offer small dried foods plus live or frozen brine shrimp nauplii, moina and grindal worms. Never feed large or hard foods that could harm their small mouths.1
How much space does a Coral Red Pencilfish need?
A tank of at least 90 cm length (about 81 litres) is needed, with dense planting, wood and leaf litter to break sightlines. This gives each male his own territory.13
What temperature, light or water does a Coral Red Pencilfish need?
Keep water at 24-28°C, pH 4.0-7.0, and hardness 1-5 dGH. They need very soft, acidic water with gentle filtration and stable conditions.1
How often should I clean a Coral Red Pencilfish's home?
Furry Diary's plan suggests a weekly 25% water change, weekly glass cleaning, and a monthly filter rinse using old tank water. Regular water testing is also recommended. Pet Wiki plan
Can a Coral Red Pencilfish live with others?
Yes, they are peaceful toward other fish but shy due to their small size. Best kept in a group of 10 or more with calm companions like Apistogramma, and plenty of cover.13
How long does a Coral Red Pencilfish live?
Lifespan varies depending on care and environment. For specific details, ask a good breeder or an exotic-pet vet.
Can I handle a Coral Red Pencilfish?
Handling is not recommended as it stresses the fish and can damage their delicate scales. Always use a soft net if you need to move them.1
Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.
You might also like
Where this comes from
Every fact on this page has a numbered source. Spotted an error? [email protected].
- Nannostomus mortenthaleri - Seriously Fish seriouslyfish.comused for origin, size, care, diet, behaviour, history
- Nannostomus mortenthaleri summary - FishBase fishbase.seused for size, IUCN, etymology, names
- Nannostomus - Wikipedia en.wikipedia.orgused for body shape, genus lifespan
Checked 2026-09-30. Text is written in our own words from these sources.