Blackline Rasbora

Geographic Origin and Biotope: Widely distributed in the Mekong and Chao Phraya river basins, as well as the Malay Peninsula. Commonly inhabits slow-moving rivers, irrigation canals, swamps, and ponds, demonstrating enormous environmental adaptability.

Taxonomy and Morphology: A classic member of the Cyprinidae family and the Rasbora genus. It has a perfectly hydrodynamic (torpedo-like) shape, ideal for constant mid-water swimming, and reaches 5-6 cm (2.4 inches) in length as an adult.

Social Behavior: Incredibly peaceful and a formidable swimmer. Like all classic rasboras, it MUST live in schools of at least 8-10 individuals to exhibit typical schooling behavior (synchronized swimming). Totally harmless to other species, it will tirelessly occupy the mid-to-upper levels of the tank.

Coloration and Sexual Dimorphism: The back is light olive-green. Its unmistakable hallmark is the thick ink-black band that cuts the flank in half from the gill cover to the tail, topped by an equally thick, brilliantly glowing yellow-gold stripe (hence its other name, 'Brilliant Rasbora'). The base of the caudal fin is often flushed with deep red. Adult females are noticeably deeper-bodied and heavier, with a prominent silver belly; males are streamlined with higher color contrast.

Tank Setup: Being a tireless horizontal swimmer, it requires a tank of at least 80 cm (32 inches) in length. Perfect when paired with dense forests of Cryptocorynes and Java Fern on the sides, leaving a massive open space in the center. They highly appreciate a moderate filter flow, which stimulates the school to swim against the current. Seal the lid: they are notorious jumpers.

Feeding and Diet: Omnivores with a strong insectivorous leaning in the wild. In captivity, they literally accept everything with great enthusiasm: floating flakes, slow-sinking micro-pellets. Fruit flies (Drosophila) and frozen bloodworms are excellent for boosting tail colors and surface hunting instincts.

Water Quality: One of the hardiest Rasboras in the world. They tolerate water hardness up to 15 GH and wide pH ranges (6.0 - 7.5). They adapt extremely well to dechlorinated tap water, making them ideal for beginners. Optimal temperature is between 22 and 26°C (72-79°F).

Compatibility and Cohabitation: The quintessence of a community fish. Marries wonderfully with small (non-nippy) barbs, Danios, Corydoras, Otocinclus, and peaceful Dwarf Cichlids. The only warning: they are such voracious eaters that they might steal all the food from shy or slow-moving fish (like Gouramis).

Aquarium Reproduction: Egg-scatterer species. Very easy: in dimly lit tanks with moss, they will scatter thousands of small transparent eggs. Naturally, they will devour their own caviar if the tank is not designed to remove the parents after spawning.

Risks and Diseases: Bulletproof fish. The only serious risk is finding them dried up on the floor due to a nocturnal jump caused by lights turning off suddenly without sunrise/sunset transitions.