Max Size: 4cm

Three Lined Pencilfish (Nannostomus trifasciatus)

Three Lined Pencilfish are relatively peaceful fish. Even though they are sociable by nature, they are a shoaling rather than a schooling species with rival territorial males sparring regularly during daytime hours establishing and defending small territories. As a result, these Pencilfish are more aggressive than most congeners, and severe injury or even death may occur in confined spaces. For this reason, you should use a spacious aquarium, and the decor should be arranged so that plenty of broken lines of sight are supplied.

It would be best if you brought at least ten individuals, preferably more, because when these fish are kept in more significant numbers, any aggression will be spread between individuals. In addition, the fish will be more confident and will exhibit more natural behaviour.

Ideal tankmates for Three Lined Pencilfish can include similarly-sized, peaceful Characids as well as smaller Catfish species. You can also combine these fish with smaller Rasboras, Barbs and Dwarf Gouramis. In addition, These Pencilfish also make an excellent dither fish for Apistogrammas and other Dwarf Cichlids as they tend to inhabit the middle-to-upper levels of the aquarium and do not predate on fry. However, calm surface-dwellers such as hatchet fish are best avoided, as are larger and more boisterous species, especially in a smaller aquarium.

Keeping Three Lined Pencilfish in a heavily-planted aquarium with a dark substrate would be better. Floating plants are also a helpful addition, as is dried leaf litter and driftwood branches. These fish only need moderate water movement; therefore, a small air-powered sponge filter is more than adequate.

The Three Lined Pencilfish is a small fish with a small mouth that may or may not possess an adipose fin. Most pencilfish have distinctive daytime and nighttime colour patterns, and this species is no exception.

During the day, they have three black longitudinal stripes that run the entire length of the body, and at night, three prominent dark spots appear on the sides of the fish, extending from their back to their belly. In addition, these pencilfish have a greenish-gold colour on their back and sides, and their stomachs are silver. The dorsal, anal, pelvic, caudal fin and gill cover display red blotches that vary in size depending on where they are from.


Three Lined Pencilfish
Three Lined Pencilfish
Quick Facts
Scientific NameNannostomus trifasciatus
Other NamesThree-stripe Pencilfish
OriginsBolivia, Brazil, Colombia, Guyana, Peru
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 10+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH5.5 - 7.0
GH2 - 8
TDS18 - 215
75 - 82℉
23.9 - 27.8℃


In the home aquarium, the Three Lined 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.

Sexual Dimorphism

Distinguishing between the male and female Three Lined Pencilfish can be somewhat challenging as different individuals can have various patterning depending on where they originate. However, males typically have an additional row of red spots in the gold area between the middle and upper stripes. In addition, they are usually slightly slimmer and more colourful than females, but once again, this is irregular.

Other Pencilfish of interest

Barred Pencilfish(Nannostomus espei)
Cenepa Red Pencilfish(Nannstomus sp)
Coral Red Pencilfish(Nannostomus mortenthaleri)
Dwarf Pencilfish(Nannostomus marginatus)
Golden Pencilfish(Nannostomus beckfordi)
Hockeystick Pencilfish(Nannostomus eques)
View all Pencilfish
Date Added: 04/02/2022 13:19:47 - Updated: 08/08/2022 15:51:03