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Maximum size : 6 cm

Blackline Tail Tetra - Moenkhausia costae : Complete Fish Profile & Care Guide

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Blackline Tail Tetras (Moenkhausia costae) are not only peaceful but also highly sociable community fish, making them a delightful addition to any aquarium. In addition, these Tetras boast remarkable hardiness, allowing them to thrive in a wide range of water conditions. However, ensuring that your aquarium is equipped with a secure, tight-fitting lid to prevent any unexpected escapades is important, as these energetic fish are known for their jumping tendencies.

To witness the true beauty of Blackline Tail Tetras, keeping them in a larger group of at least six individuals is recommended. This enables them to exhibit their natural schooling behaviour and enhances the vibrancy of their colours, particularly during their beautiful courtship rituals. While these Tetras can comfortably coexist with various species in a community aquarium, it is advisable to avoid housing them with species sporting elaborate finnage, as the Tetras may display some nippiness.

Ideal tank mates for Blackline Tail Tetras include other South American characins and bottom-dwelling fish. However, it is crucial to avoid placing them with significantly larger or more aggressive species, as these conditions may lead to stress and food competition among the inhabitants. Creating a densely planted aquarium with a dark substrate and background will beautifully accentuate the subtle hues of these Tetras. Providing ample swimming space and employing subdued lighting will further enhance their overall well-being.

Adorned with a semi-translucent silvery to green sheen on their bodies and gracefully transparent fins, Blackline Tail Tetras exhibit an exquisite stripe pattern that runs diagonally through their caudal and anal fins. This distinguishing feature adds a touch of elegance to their appearance, capturing the attention of any observer.

Blackline Tail Tetra Photos

Sexual Dimorphism

Differentiating between male and female Blackline Tail Tetras can pose a moderate challenge. Males typically exhibit distinct characteristics that set them apart from females. They are slightly smaller in size and boast more vibrant and vivid colouration. Additionally, their body shape tends to be slender rather than rounded. Conversely, females possess a subtle, less intense colouration and are generally larger in size, with plump and round stomachs. These distinguishing features provide valuable cues to identify the male and female individuals within the species.

Quick Facts

Scientific NameMoenkhausia costae
Year Described1907
Other NamesCostae Tetra
Max Size6 cm
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 6+
LifespanUp to 5 Years

Water Parameters

Water TypeFreshwater
PH6.0 - 7.5
GH5 - 18
TDS18 - 268
72 - 79
22 - 26

Natural habitat

Regrettably, comprehensive information on the natural habitat of the Blackline Tail Tetras remains scarce. Nevertheless, our understanding indicates that these captivating fish are endemic to the São Francisco and Itapicuru Rivers in the eastern region of Brazil, South America. Within these picturesque waterways, the Blackline Tail Tetras prefer the enchanting confines of shallow, vegetation-rich tributaries. Their habitat choice reflects their affinity for the nurturing embrace of densely populated aquatic flora. While further exploration is required to unravel the intricacies of their natural surroundings, their presence in these captivating river systems offers a glimpse into their captivating existence.

 São Francisco River - Brazil
Brazil Flag

How to breed the Blackline Tail Tetra

Regrettably, successful breeding of the Blackline Tail Tetra in home aquariums remains uncharted territory, and specific information regarding their breeding habits is currently unavailable. However, assuming that their reproduction process may follow a pattern similar to other Moenkhausia species is plausible.

To initiate the breeding process, a separate breeding tank is essential. This environment should be dimly lit, maintain soft water conditions, and have a slightly elevated temperature compared to their typical habitat. A heavily planted setup is crucial as it offers the Tetras suitable areas for spawning and provides ample cover for the eggs. In addition, it is crucial to continue providing a nutritious diet, including live food, to ensure the health and vitality of the breeding pair.

Once the Blackline Tail Tetras are prepared for breeding, they will engage in a captivating courtship display, locking fins and executing somersault-like movements among the plants. The female will release a batch of approximately a dozen eggs at a time, followed by the male promptly fertilizing them. Spawning generally takes place in the early morning, with the female laying several hundred eggs. Removing the parents from the breeding tank immediately after spawning is imperative, as they tend to consume the eggs.

After an incubation period of approximately 24 to 36 hours, the eggs will commence hatching, and within 3 to 4 days, the fry will become free-swimming. The fry exhibits rapid growth during this stage as they navigate their new aquatic world.

While specific details on breeding the Blackline Tail Tetra are limited, diligent observation and adherence to optimal breeding tank conditions and providing a nourishing diet can enhance the chances of successful breeding and rearing of these fascinating fish.

Diet & feeding

Blackline Tail Tetras exhibit an omnivorous feeding behaviour, displaying a versatile dietary preference. These Tetras readily accept a wide range of aquarium foods, ensuring ease of feeding. While they readily consume high-quality dried foods such as granules, flakes, and pellets, augmenting their diet with live and frozen options is highly recommended to enhance their colouration and overall condition. Offering live foods like blackworms, bloodworms, daphnia, and brine shrimp can provide essential nutrients and promote optimal health for these Tetras. By incorporating a varied diet, aquarists can ensure the well-being and vibrancy of their Blackline Tail Tetras.

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