Least Rasbora

The Least Rasbora (Boraras maculatus) is a tiny, jewel-like nano fish that punches well above its size in colour and character. Its slender body glows with warm red-orange tones, set off by a distinctive dark spot behind the gills and a series of smaller dark markings tracing along the flank towards the tail. Kept in a good-sized group, their colours intensify and their synchronised, darting movements create a mesmerising display, making them a standout choice for nano and planted aquariums.

Maximum adult size: Approximately 2–2.5 cm

Temperament: Peaceful and shy when kept alone or in small numbers, but confident and outgoing in a proper shoal. Least Rasboras should always be kept in groups of ten or more, ideally with other very small, peaceful nano species, as they can easily be outcompeted or intimidated by larger or boisterous tankmates.

Difficulty of care: Easy to moderate. Least Rasboras are hardy once settled, but their small size means they are best suited to mature, well-established aquariums with stable water parameters and no larger fish that might see them as food.

Preferred Temperature: 22–28 °C

Preferred pH of water: 5.0–7.0. Least Rasboras originate from soft, acidic blackwater habitats and generally colour up best and breed most readily in soft, slightly acidic water.

Type of breeding: Egg-scatterer. Adults show no parental care and will eat their own eggs, so fine-leaved plants or moss provide useful cover for eggs and fry in a community setting. A dedicated breeding tank with soft, acidic water and dense moss greatly improves spawning success and fry survival.

Least Rasboras thrive in densely planted aquariums with subdued lighting, driftwood, leaf litter and gentle water movement, closely mimicking their natural blackwater habitat. Floating plants help diffuse light and add to their sense of security, encouraging bolder, more natural behaviour and better colouration.

They are omnivorous and, due to their tiny mouths, require correspondingly small foods. High-quality micro pellets and crushed flakes form a good staple, supplemented with small live or frozen foods such as micro worms, baby brine shrimp and daphnia to support colour, condition and breeding activity.