How many Phoenix Rasboras should I keep together?

They should be kept in a group of at least 8 to 10 individuals. Being a shoaling species, a larger group makes them feel secure, encourages natural behaviours, and results in much brighter colouration.

What is the difference between the Phoenix Rasbora and the Chili Rasbora?

While very similar in size and base colour, you can tell them apart by their markings. The Phoenix Rasbora (*B. merah*) has a broken, oval-shaped dark blotch on its side, often surrounded by a red halo. The Chili Rasbora (*B. brigittae*) has a solid, continuous dark stripe running down its body.

Why are my Phoenix Rasboras pale and hiding?

Paling colours and hiding usually indicate stress. This could be due to a group size that is too small, water parameters that are too hard or alkaline, aggressive tankmates, or an aquarium that is too brightly lit and lacks sufficient plant cover and tannins.

Can I keep them with a Betta fish?

It carries significant risk. While they share similar water requirements, Phoenix Rasboras are so small (under 2 cm) that a large or particularly aggressive Betta might view them as food. If attempted, the tank must be heavily planted and you should have a backup plan.

Do I need to use botanicals and leaf litter?

While they can survive without them, botanicals like Indian almond leaves are highly recommended. They release tannins that lower the pH, recreate the fish's natural blackwater habitat, and help bring out their stunning red colouration.

FreshwaterTropicalIntermediate

Phoenix Rasbora

Boraras merah

A stunning, jewel-like nano fish native to the blackwater peat swamps of Borneo, prized for its fiery red halo markings.

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Ideal Conditions

Temperature: 20 – 28 °C
pH range: 4 – 6.5
Hardness: 1 – 5 dGH
Adult size: 1.5 – 2 cm
Nano tank: 25 litres+
Lifespan: 3 – 5 years
Diet: Micro-predator/Omnivore
Water flow: Low
Preferred setup: Densely planted blackwater setup with leaf litter, driftwood, and subdued lighting.

About the Phoenix Rasbora

The Phoenix Rasbora (*Boraras merah*) is one of the smallest species available in the aquarium trade, reaching a maximum length of just 2 cm. Its specific epithet 'merah' translates to 'red' in Indonesian, reflecting the brilliant, fiery colouration dominant males develop. Endemic to the highly acidic peat swamps of southern Borneo, these fish are deeply tied to blackwater environments characterised by tea-coloured, tannin-rich water. Due to their minute size and specific water chemistry requirements, they are best suited to dedicated nano aquariums or carefully planned micro-communities.

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Where Phoenix Rasbora comes from

Native range

Southeast Asia, Borneo

Countries / regions

Indonesia

Habitat

Highly acidic blackwater streams and peat swamps beneath forest canopies.

Primarily found in the Jelai Bila river basin in southern Borneo.

Similar species

Chili Rasbora
Boraras brigittae
Dwarf Rasbora
Boraras maculatus
Exclamation Point Rasbora
Boraras urophthalmoides

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Cherry Shrimp
Neocaridina davidi
Shrimp are too large to be eaten by the rasboras, and the rasboras are peaceful enough not to bother them, making an excellent nano community.
Great
Pygmy Corydoras
Corydoras pygmaeus
Both are exceptionally peaceful, appropriately sized for nano tanks, and occupy different levels of the water column.
Great
Lambchop Rasbora
Trigonostigma espei
Shares identical blackwater requirements and a peaceful temperament, forming complementary mid-water shoals.
Great
Betta Fish
Betta splendens
While they share similar environmental needs, a particularly aggressive or large Betta might view these tiny rasboras as food.
Compatible with caution
Angelfish
Pterophyllum scalare
Angelfish grow significantly larger and will easily predate on fish as small as the Phoenix Rasbora.
Not recommended

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