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Maximum size : 6 cm

Black Line Rasbora - Rasbora borapetensis : Complete Fish Profile & Care Guide

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The Blackline Rasbora (Rasbora borapetensis) is a robust and hardy freshwater fish with a peaceful demeanor that makes it an excellent addition to any temperate aquarium. These little swimmers are widely distributed and thrive in environments with slow-moving water and ample aquatic vegetation. What makes the Blackline Rasbora truly captivating is their natural inclination to school together in a tight formation, darting back and forth throughout the middle and upper regions of the tank. It's a mesmerizing sight to behold! To fully appreciate the captivating beauty of this species, a mature aquarium with abundant vegetation is recommended. The vibrant hues of this aquatic species are known to intensify when they are comfortably settled in a well-planted environment. In order to enhance their natural colors, it is recommended to use a dark substrate and background options, complemented by spindly driftwood and shady caves. It is crucial to consider the compatibility of tankmates to ensure optimal cohabitation. Selecting species of similar size and temperament that prefer soft, acidic water conditions will facilitate a harmonious aquarium community. Furthermore, a gentle flow rate is essential as these fish are accustomed to sluggish waters, though efficient filtration is still necessary to maintain a healthy aquatic environment. These silver beauties are adorned with a striking, dark brown to black mid-lateral stripe that runs from the gill opening all the way to the front of the caudal fin base. Adding to their allure is a golden bar above the dark stripe and a vibrant red caudal fin that adds a splash of color to any aquarium. If you're looking for a visually stunning and peaceful species to add to your aquarium, the Blackline Rasbora is an excellent choice. With their streamlined bodies and captivating coloration, they're sure to be the star of your aquatic community.

Black Line Rasbora Photos

Sexual Dimorphism

Distinguishing between male and female Blackline Rasboras can prove to be quite challenging as the two sexes bear a striking resemblance. However, with a keen eye, subtle differences can be observed. Females are characterized by their relatively broader, deeper bodies, and a whitish underbelly. In contrast, males are generally more slender, smaller, and have a creamy-yellow or reddish-colored belly.

Quick Facts

Scientific NameRasbora borapetensis
Year Described1934
Other NamesRed-tailed Rasbora, Bora Bora Rasbora, Brilliant Rasbora, Borapet Rasbora
OriginsThailand Cambodia Laos Vietnam Malaysia China
Max Size6 cm
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 6+
Lifespan5 - 7 years

Water Parameters

Water TypeFreshwater
PH6.5 - 7.0
GH5 - 12
KH3 - 7
71 - 79
21.7 - 26.1

Natural habitat

Blackline Rasboras can be found in the majestic Mekong and Chao Phraya Rivers, as well as the Mae Klong in western Thailand. But that's not all - they've also been spotted in Cambodia, Laos, Vietnam, Peninsular Malaysia, and China. This intriguing species even extends its reach into the Philippines and the Sunda Islands, covering parts of Malaysia, Indonesia, Brunei Darussalam, and Singapore in Southeast Asia. Blackline Rasboras thrive in shallow, slow-flowing, almost still waters that are thickly vegetated and turbid. You can observe them in ditches, ponds, drains, canals, streams, swamps, and reservoir margins. Don't miss out on the chance to witness these amazing fish in their natural environment!

How to breed the Black Line Rasbora

The Blackline Rasbora is a continuous egg-scattering spawner, with a unique spawning method. Unlike other Rasboras, their eggs are scattered among the leaves of plants rather than being open-water egg scatterers. To induce spawning, the fish should be conditioned with small, frequent live food offerings for approximately four weeks. This will not only bring out the best color in males but also encourage females to spawn. A spacious tank is essential for breeding as part of the courting ritual involves a vigorous pursuit. The water conditions should be slightly harder than the average, with a decreased acidity and raised temperature. While filtration is not necessary, a small air-powered sponge filter or peat filtration can be added. Spawning typically occurs in the early hours of the morning, with the male embracing the female in a side-by-side position as she scatters the eggs among the leaves of plants. After each spawning, the female will seek out a hiding area until the next drop. Once spawning has finished, the adult fish should be removed to prevent them from consuming the eggs. The fry will hatch within 3 to 4 days and become free-swimming around three days later. Feeding the fry with infusoria, Paramecium, or powdered food for the first few days is recommended. As the fry grow, they will quickly transition to baby brine shrimp.

Diet & feeding

When held in confinement, Blackline Rasboras demonstrate a willingness to consume dehydrated nourishment of an appropriate size, such as flakes, granules, and pellets, which should be considered a fundamental component of their dietary intake. However, it is crucial to supplement their regimen with regular feedings of diminutive live or frozen sustenance, including artemia, tubifex, bloodworm, mosquito larvae, and daphnia, on a daily basis. Such provisions will promote optimal health, growth, and pigmentation of the fish, while also encouraging spawning behavior.

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