Phoenix Rasbora (Boraras merah)

Boraras merah is native to blackwater peat swamp streams and forest pools of southern Borneo, Indonesia, where it inhabits the most extreme soft, acidic blackwater environments — water with pH values as low as 3.5–4.5, virtually zero mineral content, and dark amber coloration from dissolved tannins and humic acids.

Reaching only 2–2.5 cm, B. merah is among the smallest aquarium fish. Males display extraordinary vivid crimson-red to orange-red coloration across most of the body, complemented by a bold black spot centered on the flank and dark horizontal stripe markings. Females are slightly paler and larger-bodied when gravid. Both sexes display the characteristic Boraras body shape with a distinctive dark lateral marking.

The common name 'Phoenix Rasbora' reflects the vivid, flame-like red coloration of well-conditioned males. The species is closely related to and sometimes confused with the Chili Rasbora (B. brigittae) — the key difference is the bolder, more clearly defined black spot pattern of B. merah versus the more streaked pattern of B. brigittae.

In densely planted blackwater aquariums with dark substrate, Java moss, and Indian almond leaves, groups of B. merah create some of the most visually stunning displays available in the freshwater aquarium hobby.

Phoenix Rasboras demand authentic blackwater conditions: pH 4.0–6.5, hardness 1–4 dGH, and temperatures 23–28°C. Tannin-rich water achieved through driftwood, Indian almond leaves, dried botanicals, and peat filtration — or RO water blending — is essential for best health and maximum color intensity.

A minimum 30-liter planted nano aquarium with dark substrate, extensive fine-leaved plants (Java moss, Rotala, Staurogyne), driftwood, dried leaf litter, and floating plants for dim, diffused surface lighting creates ideal conditions. Very gentle sponge filtration.

Feed micro-sized foods only: baby brine shrimp nauplii, micro worms, daphnia, and micro pellets. Their tiny mouths require extremely small food particles. Feed 2–3 times daily in small amounts. Varied protein-rich diet enhances the crimson coloration.

Phoenix Rasboras are entirely peaceful and safe with freshwater shrimp (Neocaridina, Caridina), other Boraras species, small Corydoras, and similarly-sized nano fish. Any fish with a mouth larger than approximately 2 cm is a potential predator.

Keep in groups of at least 15–20 for impressive collective coloration. Regular small water changes (15–20% twice weekly) with soft, acidic water maintain the blackwater conditions required.