Freshwater Fish · Rasboras
Chili Rasbora
Boraras brigittae
Chilli-red speck from Borneo's peat swampsIntermediate
- Lifespan
- 4-8 years
- Size
- 1.5-2 cm / 0.6-0.8 in
- Social needs
- Shoaler; keep 10+ together
- Time
- Low-moderate; daily feeding, weekly water change
- Cost
- Low-Medium
- Diet
- Micro-predator; micro pellets, live and frozen micro-foods
Overview
What is this animal?
- The chili rasbora is a miniature cyprinid from the tannin-stained peat swamps and blackwater streams of southwestern Borneo, where males glow deep chilli red along a dark lateral stripe.
- At 1.5 to 2 centimetres fully grown it is among the smallest fish in this guide, noticeably tinier than an ember tetra and a fraction the size of a harlequin rasbora.
- Despite the common name it is not a true Rasbora but a Boraras, a genus of dwarfed species built for still, acidic water.
- Much stock is still wild-caught from habitat under pressure from peatland drainage, and those imports arrive small, thin and easily stressed, though captive-bred chilis are increasingly available and settle in far more readily.
- It is an intermediate fish for a mature, planned tank, not a first fish for a new aquarium, and if your tank is younger than a few months the honest advice is not yet.
- Ask your store whether stock is captive-bred, and favour it when offered.
Temperament
- Chilis are peaceful and completely harmless, forming a loose shoal in which males claim tiny display territories and spar with flared fins, all bluff and no damage.
- A group of ten or more spreads the sparring, builds confidence and produces the constant midwater activity and colour that a nervous group of six never shows.
- Tankmate choice is the hard part, because almost everything in the hobby can swallow or outcompete them, including peaceful staples like harlequin rasboras and bettas.
- Adult dwarf shrimp are safe with them, so the best setups are a species-only shoal or a pairing with dwarf shrimp and at most one other Boraras-sized species, though the tiniest newborn shrimplets may occasionally be picked at.
- If a planned community includes anything over about 3 centimetres, the chilis belong in a different tank.
A good fit for
- Mature planted nano and blackwater aquariums
- Species-only shoals with real presence
- Dwarf-shrimp tanks needing a genuinely shrimp-safe fish
- Aquascapers wanting a tiny, vivid centrepiece
- Keepers ready to step beyond beginner fish
Common mistakes to avoid
- Adding them to a new or immature tank
- Hard, alkaline water dulling colour and shortening lives
- Skipping slow drip acclimation for wild-caught arrivals
- Tankmates big enough to swallow them, which is most fish
- New fish refusing dry food without live micro-foods
- Open-topped tanks, as they jump
Enclosure
Minimum 20 litres (5 US gallons) — for a group of 10
Cannot be kept alone. The minimum is 10, and the space above is for that group.
- Keep a shoal of ten or more in a mature, densely planted aquarium of at least 20 litres (5 gallons), with 40 litres (10 gallons) giving far more stable water and room for a larger group.
- Heat the tank to 24-28C (75-82F) and aim for blackwater styling: dark substrate, driftwood, leaf litter and tannins that echo the peat swamps and make the red glow.
- Flow should be very gentle, and an air-driven sponge filter suits them better than a powerful internal filter.
- They want soft, acidic water, ideally pH 5.0-6.5 and low hardness, though stable slightly-acidic conditions are workable.
- Stability matters more than chasing exact numbers, because a few litres of water buffers swings poorly and these tiny bodies absorb every mistake.
- Never add them to a freshly cycled tank, and fit a tight lid, as they can jump through surprisingly small gaps.
Supplies
Setup
- Tank and stand
- Filter
- Heater and thermometer
- Substrate, plants and decor
- Liquid test kit
- Dechlorinator and starter supplies
Ongoing
- Quality micro-pellet or fine flake
- Frozen daphnia and cyclops
- Frozen or live baby brine shrimp
- Frozen bloodworm (to be chopped fine)
- Small scissors or blade for chopping frozen food
- Fine net for removing leftovers
- Small feeding spoon
Safe substrate: Inert aquarium gravel · Fine, smooth sand · Aquasoil for planted tanks
Care routine
Daily
- Check temperature and equipment
- Feed a fine-grained food
- Head-count and look everyone over
Weekly
- Top up evaporationevery 3 days
- Clean glass and clear algae
- Count the school
- Test the water
- Water change and gravel vacuum
Monthly
- Trim and thin the plantsevery 2 weeks
- Check supplies and reagent dates
- Rinse the filter media
Less often
- Replace chemical filter media (Carbon/Purigen)every 2 months
Vet: Quarterly review with a new-stock check — every 3 months
Top resources for more info
Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.
YouTubers
Girl Talks FishCare how-tos by fish type, tank setup and beginner mistakesAquarium Co-OpSpecies care guides, filtration and fish health (run by a retailer)Prime Time AquaticsSpecies profiles, stocking and water chemistry explained plainly
Sites
Go deeper
Diet
- Chilis are micro-predators that pick zooplankton and tiny invertebrates from the water column, and their mouths are minute even by nano-fish standards.
- Powdered food, finely crushed flake and the smallest micro-pellets form the dry staple, but freshly imported wild fish often refuse dry food entirely at first.
- Live or frozen baby brine shrimp, microworms, cyclops and small daphnia are the reliable way to get new arrivals feeding and coloured up.
- Feed small amounts once or twice a day, offering only what disappears within a minute or two.
- Anything sized for ordinary community fish is too large, so check that every fish in the shoal is actually eating rather than mouthing and spitting food.
Health
- The risky period is the first month, because wild-caught chilis arrive stressed and may carry internal parasites that show as wasting despite eager feeding.
- Drip-acclimatise them slowly over an hour or more, quarantine new arrivals, and expect washed-out brown fish to need weeks of quiet, tannin-stained water before the red returns.
- Ich and fin rot follow chilling or unstable water, as with any small fish.
- Once settled in a stable, soft, mature tank they are surprisingly durable and largely trouble-free.
- Do gentle weekly partial changes with temperature-matched water rather than infrequent large ones, since big parameter swings shock a fish this size.
- Daily observation is your early-warning system, because a two-centimetre body leaves no margin once illness takes hold.
Is your enclosure big enough?
Minimum volume20 litres (5 US gallons)
CompanyCannot be kept alone. The minimum is 10, and the space above is for that group.
Is this urgent?
In a fish tank the patient is usually the water. Test before you treat — dosing a healthy tank for a disease it does not have makes things worse.
Go now
Any detectable ammonia or nitrite in a stocked tankLarge water change now with dechlorinated, temperature-matched water. Stop feeding. Test again in 12 hours. Both are directly toxic. How toxic the ammonia reading is depends on pH and temperature, so the same number can be harmless or lethal.
NowFish gasping at the surface, or crowding the filter outflowIncrease surface agitation immediately, then test the water. Either the oxygen has crashed or the gills are being chemically burned. Both are hours-scale problems.
NowSudden deaths, more than one fish in a dayTest ammonia, nitrite, nitrate and temperature before doing anything else. Do not add medication yet. Multiple simultaneous deaths point at the water or the equipment, not at a pathogen.
NowToday
Flashing — repeatedly scraping against decor or substrateTest the water, then look closely for parasites. Irritation is either chemical or parasitic; the test tells you which before you medicate.
TodayWhite salt-grain spots over the body and finsBegin the appropriate treatment today and check the temperature. The parasite's life cycle is temperature-driven, and it multiplies with every cycle you wait.
TodaySoon
Clamped fins, hiding, or refusing food for more than two daysTest the water and review recent changes. Usually the earliest visible sign of a parameter drifting.
A few daysNever add a new fish to a tank that is not fully cycled, and never treat blind. A test kit is cheaper than the fish.
This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.
What it really costs
Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.
Bedding and substrate
Substrate in an aquarium is a filter as much as a floor. Most of the biology lives in and on it.
Safe
Inert aquarium gravelRinse thoroughly before use. Grain size should be too large to swallow and too small to trap food.
safeFine, smooth sandCorrect for corydoras, kuhli loaches and anything that sifts. Their barbels wear away on sharp gravel.
safeAquasoil for planted tanksExcellent for plants, but it leaches ammonia for the first weeks. Cycle around it; do not stock into it.
safeBare bottomLegitimate for quarantine and grow-out tanks. Easy to clean, but it holds far less biological filtration.
safeWith a caveat
Crushed coral or aragoniteDeliberately raises hardness and pH. Correct for rift-lake cichlids, wrong for soft-water species.
with a caveatVery deep sand bedsAnaerobic pockets form below about 5 cm in still sand. Either keep it shallow or keep it stirred.
with a caveatPainted or coated gravelUsually fine, but coatings chip. Test a handful in a jar for a week first.
with a caveatNever
Sharp or angular gravel with bottom-dwellersWears down barbels and leads to infection in corydoras and loaches.
neverAnything containing metal, limestone of unknown origin, or shells in a soft-water tankSlowly alters chemistry in ways that are hard to diagnose later.
neverThis is our general list for freshwater fish. We have not built one specific to Rasboras yet.
My kit says 0.25 ppm. Is that dangerous?
A liquid kit measures total ammonia, but only the un-ionised fraction is really toxic, and that fraction is governed by pH and temperature — each whole pH unit multiplies it roughly tenfold. So the same reading can be nearly harmless in one tank and lethal in another; this works out which one you are in.
Compare with other animals
The same axes for every animal, side by side — the way the guides are written makes that a fair comparison rather than two articles.
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Rasboras, side by side
Same axes, same care guides — the honest way to choose between types.
See all Rasboras side by side →
