Max Size: 3.5cm

Coral Red Pencilfish (Nannostomus mortenthaleri)

The stunning Coral Red Pencilfish are a relatively new addition to the fishkeeping hobby and were only accurately described in 2001. This pretty little fish was first considered a sub-species of the Dwarf Pencilfish but was later recognised as its own distinct species.

The Coral Red Pencil fish is a beautiful, petite, active and personable fish that makes a great addition to a nano or well-planted aquarium. However, these fish do not make an ideal member of a typical community aquarium due to their small size and somewhat timid nature.

If you wish to keep Coral Red Pencilfish with other species, they should ideally be small, non-aggressive species such as smaller Tetras, Micro Rasboras and dwarf Barbs. You can also house these fish with Corydoras Catfish and amicable Plecos. These Pencilfish also make an ideal dither fish for Apistogrammas and other Dwarf Cichlids as they typically inhabit the middle to upper areas of the aquarium and do not actively predate fry.

Though sociable by nature, Coral Red Pencilfish are a shoaling rather than schooling species with rival territorial males sparring regularly during the day. For this reason, you should use a spacious aquarium and arrange the d├ęcor, so plenty of broken lines of sight are provided. In addition, it would be best to keep these fish in a group of at least 10, preferably more. Keeping these fish in larger groups will not only prevent aggression on single individuals but will make the fish feel safer, leading to more natural behaviour and a better display.

The ideal aquarium setup for Coral Red Pecilfish would be a heavily planted aquarium with a dark substrate and sheltered areas to help reduce skittishness and offer refuge for sub-dominant individuals. Floating plants, driftwood branches and dried leaf litter are all useful, and you will need gentle filtration. An air-powered sponge filter is more than adequate. These fish require stable water conditions; therefore, you should never add them to a biologically immature aquarium.

The Coral Red Pencilfish is small and slender, with the males having red colouration covering their entire body and fins, whereas the female's body is pinkish. In addition, these fish have two prominent thick lateral black stripes to contrast, and the anterior portion of the dorsal fin in males is white at the base.

Recently, a Super Red coral Pencilfish has been observed making its way into the hobby. However, it has yet to be formally described as a variant of the coral red pencilfish and is currently marked as Nannostomus sp. "Albertini Super Red". as this beautiful gem may turn out to be a new species of pencilfish entirely.

Coral Red Pencilfish (Nannostomus mortenthaleri) Video

Coral Red Pencilfish - Nannostomus Mortenthaleri - Rare Freshwater Nano Aquarium Fish Profile


Coral Red Pencilfish
Coral Red Pencilfish
Coral Red Pencilfish
Coral Red Pencilfish
Coral Red Pencilfish
Albertini Super Red
Quick Facts
Scientific NameNannostomus mortenthaleri
Year Described2001
Other NamesPeruvian Red Pencilfish, Ruby Red Pencilfish, Red Arc Pencilfish,
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 5+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH4.0 - 7.0
GH1 - 12
TDS18 - 90
75 - 82℉
24 - 28℃

Natural Habitat

Nanay River
Rio Tigre


In the home aquarium, the Coral Red Pencilfish will readily accept most good quality dried foods such as granules, flakes and sinking pellets. These modern food products have been developed to provide all adequate nutrition to maintain your fish's health and dietary requirements.

Providing additional foodstuffs such as live, frozen, and freeze-dried meals such as bloodworm, daphnia, and tubifex once or twice a week will provide additional benefits to your fish's health and well-being but is not a must for this fish.

It should be noted that bloodworms should only be given as an occasional treat and should not be used as the staple diet as they are difficult for fish to digest and can potentially cause blockages.

This fish is an omnivore in the wild, meaning it will consume some vegetable matter. Although most modern fish foods take this into account and include them in their products, you can still supplement your fish's diet with blanched vegetables such as spinach, broccoli, and zucchini. Ensure you do not overfeed your fish and remove any leftovers the following day.

Tank Mates

10 interesting tank mate ideas for the Coral Red Pencilfish could include:

Agassizs Corydoras(Corydoras agassizii)
Domino Tetra(Neolebias powelli)
Eight Banded False Barb(Eirmotus octozona)
Golden Dwarf Barb(Pethia gelius)
Honey Blue Eye Rainbowfish(Pseudomugil Mellis)
Panda Loach(Yaoshania pachychilus)
Peacock Gudgeon(Tateurndina Ocellicauda)
Purple Pencilfish(Nannostomus rubrocaudatus)
Rainbow Copella Tetra(Copella vilmae)
Spotted Blue Eye Rainbowfish(Pseudomugil gertrudae)

Sexual Dimorphism

It is simple to differentiate between the male and female Coral Red Pencilfish. Adult males are slimmer, far more vibrantly coloured than females and display a white marking at the anterior dorsal-fin base from a young age. Another way to determine the sex of this species is to watch their behaviour; males will frequently present and nip at each other, while the females are very docile.

Other Pencilfish of interest

Barred Pencilfish(Nannostomus espei)
Cenepa Red Pencilfish(Nannstomus sp)
Dwarf Pencilfish(Nannostomus marginatus)
Golden Pencilfish(Nannostomus beckfordi)
Hockeystick Pencilfish(Nannostomus eques)
Purple Pencilfish(Nannostomus rubrocaudatus)
View all Pencilfish
Date Added: 06/08/2020 - Updated: 08/08/2022 15:41:30