Freshwater Fish
Chili Rasbora
The smallest commonly kept schooling fish in the hobby -- a vivid red-orange nano fish with a black lateral stripe, reaching just over half an inch at maturity. Spectacular in large schools in nano planted tanks.
Chili Rasboras (Boraras brigittae), also known as Mosquito Rasboras, are one of the smallest schooling fish kept in the freshwater hobby, reaching approximately 0.6 to 0.7 inches at full maturity. Their tiny size belies a vivid colour -- a bright red to orange-red body with a bold black lateral stripe and black markings on the fins that create a strong graphic contrast at close range. In a school of 20 or more in a densely planted blackwater-style nano tank, the collective flash of red moving through green vegetation is a display that punches dramatically above what the individual fish size would suggest. They require soft, acidic water and are one of the more parameter-sensitive fish on this list. Not a beginner fish in the sense of tolerating a wide range of conditions, but straightforward to keep long-term in a stable, well-established soft-water setup.
4.0–7.0pH
1–5GH (dGH)
72–82°FTemperature
0.7 inMax Size
Appearance & Schooling
Tiny, Vivid, and Best in Numbers
Vivid red to orange-red body with a bold black lateral stripe and black fin markings. The colour of a healthy, well-conditioned Chili Rasbora in soft acidic water is genuinely striking -- a saturated warm red against the black stripe that reads as vivid and intentional even at the fish's very small size. Males show more intense colour than females, particularly when actively displaying. Colour fades noticeably in hard or alkaline water, which is a reliable parameter warning sign.
School of 10 minimum, 20 or more strongly recommended. The visual impact of Chili Rasboras is entirely dependent on school size. A group of 6 is barely visible in most tanks. A group of 20 or more creates a cloud of red that reads as a display element in its own right rather than background detail. Their tiny size means a school of 20 has a minimal bioload even in a 10-gallon tank.
Soft acidic water is not optional -- colour and health degrade in hard or alkaline conditions. Chili Rasboras originate from blackwater peat swamps in Borneo where the water is extremely soft and acidic. In water above pH 7.0 or GH above 8 they show faded colour, reduced activity, and shortened lifespans. This makes them ideal companions for Caridina shrimp tanks using active substrate and RO water, but a poor fit for standard hard-water Neocaridina setups.
Shrimp Compatibility
Mouth Too Small for Adult Shrimp
One of the most shrimp-safe fish available due to extremely small mouth size. Adult Chili Rasboras have mouths so small that adult Neocaridina and Caridina shrimp are entirely safe. Even mid-sized juvenile shrimp are typically too large to be consumed. The primary risk is to newly hatched shrimplets in the first week of life, which are small enough to be targeted. In a planted tank with Java Moss or Subwassertang the survival rate of shrimplets in a mixed tank is high.
Natural parameter overlap with Caridina shrimp makes this a particularly strong pairing. Both Chili Rasboras and Caridina species prefer soft, acidic water -- pH 5.8 to 6.8, very low GH and KH. A Caridina tank running RO water with active substrate is close to ideal for Chili Rasboras simultaneously. This makes the combination one of the most parameter-compatible fish-and-shrimp pairings in the freshwater hobby.
Not well-suited to hard-water Neocaridina setups. If your Neocaridina tank runs at pH 7.2 to 7.6 and GH 10 to 14, Chili Rasboras will not thrive long-term. Choose White Cloud Mountain Minnows or Celestial Pearl Danios for harder Neocaridina water instead.
Keeper's NoteA school of 30 Chili Rasboras in a blackwater-style 15-gallon tank with tannin-stained water, dark substrate, Subwassertang, and a colony of Crystal Red Shrimp is one of the most striking and most cohesive nano tank setups in the freshwater hobby. The red of the Rasboras and the red-and-white of the CRS share a colour relationship that reads as intentional, the blackwater aesthetic unifies both species visually, and the parameter requirements of all inhabitants align precisely. It is a setup that takes patience to establish but is among the most rewarding in the hobby once stable.
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