Max Size: 4cm

Purple Pencilfish (Nannostomus rubrocaudatus)

The Purple Pencilfish is relatively peaceful and can be somewhat shy. Nevertheless, these Pencilfish make a stunning addition to a planted aquarium or a blackwater biotope aquarium. Like most Pencilfish, they will do best in a group of 10 or more individuals. However, it would be better to have more females than males as they can be rough with each other, frequently sparring during the day and pressuring the females. Due to their boisterous nature, they will require a sizeable spacious aquarium, especially if you plan on keeping them with other species.

Ideally, you should maintain these fish alone or at most with small, non-aggressive tankmates such as other peaceful medium-sized Characins, Corydoras, Aspidoras, and smaller plecos. Purple Pencilfish also make an excellent dither fish Apistogrammas and other South American Dwarf Cichlids.

It would be best to keep Purple Pencilfish in a heavily-planted set-up with a dark substrate making sure you have plenty of hiding places. The hiding places will form a refuge for skittish or subdominant individuals and provide plenty of broken lines of sight. Floating plants are a useful addition, so is dried leaf litter and driftwood branches. These Pencilfish will also appreciate gentle water movement; an air-powered sponge filter will be just fine. In addition, these Pencilfish require stable water conditions so should never be introduced to an immature aquarium.

Purple Pencilfish have a bright reddish-purple colour between the dark stripes on their sides. The middle dark stripe extends to the base of the anal fin, and the dorsal and caudal fin is mainly red in males. The females have a smaller red spot, and the spacing between the primary and secondary stripes is silvery, with a reddish stripe below the direct black stripe at the rear of the body.

Tank Mates for the Purple Pencilfish

1 ideal tank mate ideas for the Purple Pencilfish include:

Ivantsoffs Blue Eye Rainbowfish(Pseudomugil ivantsoffi)
Quick Facts
Scientific NameNannostomus rubrocaudatus
Other NamesPurple Dwarf Pencilfish, Double Red Pencilfish
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 10+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH4.0 - 7.0
GH2 - 12
TDS18 - 90
75 - 82℉
23.9 - 27.8℃

Photos of the Purple Pencilfish

Purple Pencilfish
Purple Pencilfish

Natural Habitat

Purple Pencilfish are endemic to the Marano, Morona and Santiago Rivers in Peru in South America. They inhabit slow-flowing tributaries in small rivers and swampy areas, mainly in areas with dense aquatic vegetation, leaf litter and submerged woody structures.

What to feed the Purple Pencilfish

In nature, Purple Pencilfish feed on tiny invertebrates and other zooplankton. In the aquarium, these Pencilfish will readily accept dried foods of a suitable size; however, it would be better if you also provided them with daily meals of small live, frozen or freeze-dried foods such as newly hatched brine shrimp, Moina and grindal worm.

How to sex the Purple Pencilfish

It is simple to differentiate between the males and female Purple Pencilfish. Adult males are slimmer and far more intensely coloured than females, and they possess a modified anal fin, with the third to sixth rays being much thicker.

How to breed the Purple Pencilfish

Purple Pencilfish, although relatively rare, have been bred in the home aquarium. In a heavily-planted, established aquarium, small numbers of fry may start to appear without intervening. However, if you would like to increase the fry yield, a slightly more controlled approach will be required.

You can still condition the adult group together, but smaller containers should also be set up and filled with mature water. It would be better to fill much of the container with spawning mops, java moss or other fine-leaved aquatic plants and lighting and filtration is unnecessary. However, you can place a small air-powered sponge filter in the container if you prefer.

Once you have conditioned the adult fish, you should introduce one or more pairs to each container. However, if you are using more than a single pair, make sure you arrange the plants or mops so that individual territories are created. For example, if you have two pairs, make sure you place the spawning medium at either end of the tank keeping a space between them.

You can remove the adults after 2 or 3 days, and then the first fry should start to appear a day or two later.

If you ars using mops, an alternative method is to check them daily, removing and replacing them as you find any eggs and hatch the fry elsewhere.

You should initially provide the fry with Paramecium or a good quality dry food of sufficiently small grade, introducing microworm and baby brine shrimp once the babies are large enough to accept them. The fry should start to develop colouration and patterning after eight weeks or so.

Other Pencilfish of interest

Barred Pencilfish(Nannostomus espei)
Coral Red Pencilfish(Nannostomus mortenthaleri)
Dwarf Pencilfish(Nannostomus marginatus)
Golden Pencilfish(Nannostomus beckfordi)
Hockeystick Pencilfish(Nannostomus eques)
Three Lined Pencilfish(Nannostomus trifasciatus)
View all Pencilfish
Date Added: 08/02/2022 12:48:51 - Updated: 08/02/2022 13:04:21