Care guide · Freshwater · fish

Chili rasbora

Boraras brigittae

Photo: Daiju Azuma · Source · CC BY-SA 4.0Resized and compressed; no cropping or colour changes.

The chili rasbora, Boraras brigittae, is an exceptionally small fish that brings considerable activity when kept in a quiet group. Its red colour and dark longitudinal markings become particularly striking when the fish feel secure among cover and open swimming lanes. Small size does not, however, make this species suitable for every tiny container. A mature, stable aquarium and food that genuinely fits its minute mouth matter more than the appealing label nano fish. Busy or larger companions can keep the group permanently in the background without visibly chasing it. Consider food competition and predation before combining species. A species-focused aquarium with enough companions is often easier to manage than a collection of small fish with different requirements. This guide concerns Boraras brigittae, not every red Boraras sold under the same trade name.

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At a glance

Temperature: 24–26 °C
pH: 5.5–6.8
GH: 2–6 °dGH
Aquarium length: At least 45 cm
Adult size: Approximately 2 cm
Group size: At least 10 individuals
Swimming zone: Middle
Temperament: Peaceful
Cover: Plants and sheltered areas
Staple food: Fine flakes, Fine powdered food
Supplementary food: Live food, Frozen food, Finely crumbled dried natural food

Provide an aquarium from forty-five centimetres long for at least ten fish. Sixty centimetres is more comfortable, leaving additional space for plants and a larger group. Their minute body size does not justify an unfiltered vase or newly started miniature tank.

About this species

Adults reach about two centimetres standard length, excluding the tail fin. Males are often slimmer and more intensely red, while females are generally fuller. Colour also varies with age, condition and stress. A pale newcomer is not necessarily misidentified, but colour alone does not prove identity either.

Compare body shape and dark flank markings together. Boraras merah and Boraras urophthalmoides can be confused with this species. Use clear photographs and origin information rather than treating every tiny red rasbora alike. The current classification places it in Danionidae. Rasbora remains a useful common name even though the scientific genus is Boraras.

Natural habitat

Chili rasboras originate from southwestern Borneo. Forest swamps and slow or still waters rich in organic material form their known habitat. Leaves and wood stain the water, while forest and marginal vegetation reduce light. Consequently, submerged plants need not cover every part of the natural substrate.

A planted aquarium can nevertheless provide a practical equivalent: plants offer shelter and interrupt sight lines. Suitable leaves are optional, but brown water does not prove that pH and hardness are correct. Keep quiet open spaces between dense areas so feeding and social behaviour remain observable. An exact biotope recreation and a functional care aquarium are different choices; both demand good water quality.

Aquarium and layout

Use subdued light, fine shelter and gentle water movement. A sponge filter or safely protected intake prevents small fish disappearing into filtration. Do not allow floating plants to seal the whole surface. Arrange cover so subordinate fish can leave each other's sight without entering a bare corner. Keep the aquarium covered and plan maintenance to avoid accidentally removing fish with plant trimmings or siphoned water.

Water conditions

Our practical maintenance choice is 24–26 °C, pH 5.5–6.8 and GH 2–6. Some keepers report success in harder or alkaline water, whereas other sources specifically recommend soft acidic conditions. We adopt the softer, mildly acidic profile conservatively without making extreme natural acidity compulsory.

Measure tap water before buying a group. If adjustment is necessary, it should be repeatable and gradual. Adding acid without understanding buffering is not a care plan. Carry out modest maintenance appropriate to the aquarium with prepared water and preserve biological filtration. Mistakes have rapid consequences in small tanks. Achieving the preferred numerical ranges never makes detectable ammonia or nitrite acceptable.

Behaviour and group size

A group of at least ten allows more social interaction and distributes attention between males. Small temporary territories may form during courtship. This does not justify keeping isolated pairs in undersized tanks; cover and group space are helpful.

Suitable neighbours are small, quiet and unable to swallow adult rasboras. Even a peaceful larger fish may therefore be unsuitable. Assess feeding as well: fast livebearers or energetic barbs can outcompete the group. Adult dwarf shrimp are usually left alone, but tiny shrimplets are not guaranteed protection. A mature group that constantly hides or loses weight needs its community reassessed, not automatically more fish.

Feeding

This miniature predator takes tiny invertebrates and other appropriately sized particles from the water column. Choose a complete microfood with suitable animal ingredients and a demonstrably usable particle size. Mini or tropical on the packaging is insufficient: check that the smallest fish swallow it rather than repeatedly spitting it out.

Finely crushed flakes may work provided they do not immediately disperse as uneaten dust. Small live or frozen foods, such as suitable Cyclops or young Artemia, can supplement the diet. Offer small portions across the quiet swimming area without allowing everything to sink straight to the bottom. More food cannot compensate for the wrong size. A careful species-specific recommendation may therefore contain fewer shop products than one for a larger tetra.

Breeding

Well-conditioned adults may deposit small numbers of eggs among fine structures. There is no protective parental care, and eggs or fry can be eaten. Deliberate rearing benefits from separate mature accommodation with fine plants or a suitable spawning mop and protected filtration.

First feeding is a major difficulty. Newly feeding fry initially need food smaller than Artemia nauplii. Prepare a dependable culture of suitable microscopic food and move to larger items according to actual ingestion rather than a calendar alone. Remove adults after observed spawning to reduce predation. Keep rearing conditions clean without stripping away all microfauna. A few spontaneously surviving fry are encouraging but do not demonstrate that a larger breeding project needs no preparation.