Redtail Rasbora (Rasbora borapetensis)

The Redtail Rasbora (Rasbora borapetensis), also known as the Black-Line Rasbora or Red-Tailed Rasbora, is a slender, active schooling fish from the rivers, streams, and floodplain pools of Thailand, Malaysia, and neighboring Southeast Asian countries. Its most notable feature is the vivid red-orange caudal fin that stands out against its transparent silver body and prominent black lateral stripe.

This species is a classic community aquarium fish that has been popular in the hobby for decades. It shares the peaceful, schooling nature characteristic of the Rasbora genus and is straightforward to keep in a range of water conditions. However, it shows its best colors in soft, slightly acidic water that mimics its natural lowland stream and floodplain habitat.

Redtail Rasboras are active mid-water swimmers that form tight schools when feeling secure. Keeping them in groups of 8 or more allows natural behavior to express and creates a striking visual display with coordinated schooling movement. They are compatible with a wide range of similarly-sized peaceful fish.

This species is an omnivore that accepts most standard aquarium foods readily. It is a relatively easy species to care for and is suitable for intermediate to beginner aquarists with appropriately soft, acidic water.

Water Parameters: Redtail Rasboras prefer soft to moderately soft, slightly acidic water: pH 5.5–7.0, temperature 22–28°C, GH 2–12. Tannin-stained water from driftwood or Indian almond leaves enhances coloration. They adapt to slightly harder conditions but show best colors in softer water.

Tank Setup: A 60-liter minimum for a school of 8. Plant the aquarium with fine-leafed plants, driftwood, and floating plants for natural cover. A dark substrate enhances the silver and red contrast. Gentle to moderate filtration is appropriate — they are not fond of strong currents.

Feeding: Omnivores that accept quality micro flake food, micro pellets, small frozen foods like daphnia and brine shrimp nauplii, and micro worms. Feed twice daily in small amounts. Varied diet improves health and coloration.

Tankmates: Peaceful and sociable. Ideal companions include other small rasboras, small tetras, Corydoras, and dwarf cichlids. Avoid fin-nippers and large, boisterous fish. Their peaceful nature makes them vulnerable in aggressive setups.

Health: Hardy and generally easy to maintain. Sensitive to hard alkaline water and sudden parameter changes. Keep stable soft, slightly acidic conditions. Weekly water changes of 25% maintain water quality. Monitor for ich and velvet.