Blue Line Rasbora Care Guide - Aquarium Setup, Diet & Breeding

The Blue Line Rasbora, Rasbora sarawakensis, is a small and elegant cyprinid with a slender, streamlined body. Its most distinctive feature is the vivid blue-green lateral stripe that runs along the flanks, often contrasting with a warm golden or coppery sheen on the body. In good condition, the stripe becomes especially striking when the fish are displaying or moving together.

Blue Line Rasboras are native to the island of Borneo in Southeast Asia, particularly the freshwater habitats of Sarawak, Malaysian Borneo. They are associated with clear, slow-moving forest streams and blackwater-influenced waterways surrounded by dense vegetation.

A group of Blue Line Rasboras should have at least a 60-litre aquarium, ideally measuring around 60 cm long by 30 cm wide or larger so they have room to shoal. Use a dark, fine-grained substrate with dense planting around the sides and rear, leaving open swimming space in the centre. Driftwood, leaf litter and subdued lighting can recreate their forest-stream surroundings, while gentle filtration and a covered aquarium help provide the calm conditions they prefer.

Up to around 5 cm (2 inches) in total length. Females are usually slightly larger and deeper-bodied than males.

These omnivorous rasboras should receive a varied diet of high-quality micro pellets or fine flakes supplemented with frozen or live foods such as daphnia, baby brine shrimp, cyclops and mosquito larvae. Their small mouths require appropriately sized food. Feeding small portions once or twice daily helps maintain condition without allowing excess food to accumulate.

Blue Line Rasboras are peaceful community fish and are best kept with similarly gentle species such as small rasboras, peaceful tetras, kuhli loaches, pygmy corydoras and small freshwater shrimp. Avoid large, boisterous or predatory fish, fin-nippers and aggressive cichlids, which may frighten or consume them. Their colours and confidence are strongest when they are kept in a proper shoal rather than as isolated specimens.

Blue Line Rasboras are egg-scattering fish that can be bred in a mature, densely planted aquarium or a separate breeding tank with soft, slightly acidic water. Condition the adults with small live or frozen foods, then provide fine-leaved plants or spawning mops for the eggs. Spawning usually takes place among the plants, with eggs scattered over several days. Remove the adults or protect the eggs with a mesh barrier, as the fish may eat them. The eggs generally hatch within 24 to 48 hours, and the tiny fry need infusoria or another suitably fine first food before progressing to newly hatched brine shrimp.

Males are generally slimmer and more intensely coloured, particularly when displaying, while females have a fuller body and a noticeably rounder abdomen when carrying eggs. The differences can be subtle outside breeding condition.