Phoenix Rasbora is a tiny, brilliantly colored cyprinid perfect for planted nano tanks with soft, acidic water and peaceful micro-fish communities.
Overview
Boraras merah is one of the smallest members of the family Cyprinidae, reaching only 1.5–2 cm in length. In the wild, this fish inhabits peat swamps and slow-moving backwaters of rivers on the island of Borneo (Indonesia), where the water is stained a characteristic brown color by decomposing leaf litter. The species earned its common name "Phoenix Rasbora" thanks to its vivid red-orange body coloration contrasted by a dark stripe running along the lateral line.
Despite their tiny size, Boraras merah possess a striking appearance: during spawning, males develop dramatically intensified coloration, turning them into living sparks of fire. This is a schooling fish with a peaceful temperament that thrives in the company of its own kind. In my experience, a group of 10–15 individuals in a well-planted nano tank is one of the most visually captivating displays available to an aquarist.
Tank Requirements
A tank of at least 20 liters is sufficient for keeping Boraras merah, though a 30–40 liter aquarium will allow the school to feel considerably more comfortable. Optimal water parameters are: temperature 22–28°C, pH 5.5–7.0, and general hardness (GH) 5–12. Ideally, pH should be maintained toward the lower end of the range — 5.5–6.5 — as these fish display their most vibrant coloration in slightly acidic water.
The tank should be densely planted with fine-leaved species such as Java moss, Rotala, and Bucephalandra. Floating plants on the surface (Pistia, Salvinia) help create subdued lighting. Driftwood and fallen Indian almond or oak leaves not only enhance the aquascape but also release tannins that acidify the water and recreate conditions closer to the species' natural habitat. Dark substrate is preferable, as it makes the fish look particularly striking.
Water flow should be minimal. I recommend using an air-driven sponge filter: it provides gentle filtration, does not create a strong current, and is safe for fry.
Feeding and Diet
In their natural habitat, Boraras merah feeds on microscopic invertebrates, zooplankton, and insect larvae. In the aquarium, the diet should be varied while accounting for the fish's tiny mouth.
High-quality micro-pellets and crushed flakes can form the staple diet. However, the best results — in terms of both health and coloration — come from regularly offering live and frozen foods: baby brine shrimp, microworms, Grindal worms, and daphnia. Feed 1–2 times daily in small portions that the fish consume within 2–3 minutes. Overfeeding is one of the main issues when keeping small species, so it is always better to underfeed slightly than to overfeed.
Care and Maintenance
Keeping Boraras merah is not particularly difficult and is accessible even to beginner aquarists, provided a few key rules are followed. Weekly water changes of 20–25% help maintain stable parameters. It is important to use replacement water that closely matches the tank water in temperature and chemistry — sudden fluctuations are harmful to these small fish.
Regularly test for ammonia, nitrites, and nitrates. Nitrate levels should not exceed 20 mg/L. Trim overgrown plants to preserve open swimming space at the front of the tank, while keeping the back and sides densely planted so the fish feel secure.
Boraras merah lives 3–4 years with good care. Healthy fish are active, stay together as a school, and display vivid coloration.
Compatibility
Boraras merah are exceptionally peaceful fish that should be kept in groups of at least 8–10 individuals. In a larger group, they behave more confidently, and males begin displaying their finest colors to one another, making them especially engaging to observe.
Ideal tankmates include other peaceful micro-fish: Boraras maculatus, Chili Rasbora, Emerald Dwarf Rasbora, and Ember Tetra. Pygmy Corydoras make excellent companions as they occupy the lower level of the tank and do not compete for space. Dwarf shrimp (Neocaridina) also coexist beautifully with this species.
Under no circumstances should large or active fish be added — even common Neon Tetras can prove too boisterous for these tiny fish. Any species capable of swallowing Boraras merah poses a direct threat.
Breeding
Breeding Boraras merah in the aquarium is possible but requires patience and attention to detail. For spawning, prepare a small 10–15 liter tank with soft, acidic water (pH 5.5–6.5, GH 2–5) and a temperature of 26–27°C. Place fine-leaved plants or spawning moss on the bottom — the fish deposit eggs among thin leaves and moss.
This species exhibits no parental care, so adults must be removed after spawning to prevent egg predation. Incubation takes 2–3 days, after which the larvae spend another 1–2 days absorbing their yolk sac. Initial food for the fry consists of infusoria and microscopic algae. After 7–10 days, they can be transitioned to baby brine shrimp and microworms.
Fry grow slowly and are extremely sensitive to water quality, so water changes in the rearing tank should be performed frequently but in small amounts — 5–10% every 2–3 days.