Max Size: 6cm

Blackline Tail Tetra (Moenkhausia costae)

Blackline Tail Tetras are a peaceful and very sociable community fish. These Tetras are hardy species that are tolerant of a wide range of water conditions. However, you will need to make sure that you keep these fish in an aquarium with a tight-fitting lid as they are likely to jump.

These Tetras are very active schooling fish and will thrive if kept in a larger group of at least six individuals. They will express more natural behaviour and better colours, especially when persuing the females for attention.

Blackline Tail Tetras can live in a community aquarium with many different species without difficulty. However, it would be best not to place them with species that have elaborate finnage as these Tetras can be a tad nippy at times.

Ideal tank mates for these fish would be other South American characins and bottom-dwellers. However, it would be better if you did not house these Tetras with much larger or more aggressive species otherwise, they will get stressed and outcompeted for food.

Blackline Tail Tetras prefer a densely planted aquarium containing a dark substrate and background to best show off the subtle colours of these fish. These fish also require plenty of swimming space and some subdued lighting.

Blackline Tail Tetras have a semi-translucent silvery to a green sheen on their body and transparent fins. In addition, their caudal and anal fin has a unique stripe pattern running through them that displays a perfectly even diagonal line.

Quick Facts
Scientific NameMoenkhausia costae
Other NamesCostae Tetra
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 6+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH6.0 - 7.5
GH5 - 18
TDS18 - 268
72 - 79℉
22.2 - 26.1℃


Blackline Tail Tetra

Natural Habitat

Again, unfortunately, there is little information on the natural habitat of the Blackline Tail Tetras. However, we do know that these fish are endemic to the São Francisco and Itapicuru Rivers in eastern Brazil in South America, where they inhabit shallow and heavily vegetated tributaries.

São Francisco River


Blackline Tail Tetras are omnivorous and will readily accept most types of aquarium foods. They will take high quality dried foods such as granules, flakes and pellets; however, for the most desirable colour and condition of your fish, it would be beneficial also to provide them with plenty of live and frozen foods. These can include blackworm, bloodworm, daphnia and brine shrimp.

Sexual Dimorphism

It is relatively challenging to distinguish the males from female Blackline Tail Tetras. The males are usually a bit smaller and are more brightly coloured than females, and their bodies are somewhat more slender than rounded. In contrast, the females are slightly duller, somewhat larger, and their stomachs are plumper and rounder.


Unfortunately, The Blackline Tail Tetra has not been bred in the home aquarium, and there is no information on how to breed this fish. However, these Tetras are likely to reproduce similarly to other Moenkhausia species.

Blackline Tail Tetras will require a separate breeding tank, this should be dimly lit with soft water, and the temperature will need to be raised by a few degrees higher than what they usually have. The breeding tank will also need to be heavily planted as this will provide shaded areas for them to spawn in.

For the healthiest and best fry, you will need to choose your strongest female and the best-coloured male, place them into the breeding tank, and continue to feed them with rich food; this includes live food.

When The Blackline Tail Tetras are ready to breed, they will lock fins, and when this occurs, they will carry out a somersault movement in the plants. The female will release about a dozen eggs at a time, and then the male will fertilise them.

Blackline Tail Tetras will usually spawn in the early morning, and the female will lay a couple of hundred eggs which the male will fertilise. Once this has taken place, you should remove the parents, as they will consume the eggs.

After about 24 to 36 hours, the eggs will start to hatch out, and 3 to 4 days after that, the fry will become free swimming and grow relatively quickly.

Other Tetras of interest

African Moon Tetra(Bathyaethiops caudomaculatus)
African Red Eyed Tetra(Arnoldichthys spilopterus)
Black Darter Tetra(Poecilocharax weitzmani)
Black Line Tetra(Hyphessobrycon scholzei)
Black Neon Tetra(Hyphessobrycon herbertaxelrodi)
Black Phantom Tetra(Hyphessobrycon megalopterus)
View all Tetras
Date Added: 12/10/2021 10:28:00 - Updated: 22/11/2021 16:56:45