Chili Rasboras Care Guide: Tank Setup, Feeding & Tank Mates

Chili rasboras are some of the most eye-catching fish in the freshwater hobby. They're tiny, vivid red, and absolutely mesmerizing when they school through a planted nano tank.

Quick Answer: Chili rasboras (Boraras brigittae) grow to just 0.7 inches and thrive in soft, acidic water (pH 5.5–7.0, 72–82°F). They need a heavily planted nano tank of at least 5 gallons, peaceful micro tank mates, and tiny live or frozen foods. They're best suited to intermediate keepers who can maintain stable, soft water chemistry.

What Are Chili Rasboras?

Chili rasboras (Boraras brigittae) are one of the smallest schooling fish in the freshwater hobby, maxing out at just 0.6–0.8 inches as adults. According to Fishbase, they originate from blackwater peat swamps in Borneo, Indonesia — dark, tannin-rich water with minimal dissolved minerals [1]. Males are vivid red-orange; females are slightly larger and paler.

They're also sold as mosquito rasboras. Both names refer to the same fish. Don't confuse them with ember tetras — similar in size, but a completely different genus.

Species Quick Facts

Chili rasboras are long-lived for their size. With proper care, they reach 5–6 years — well above average for micro fish [1]. That longevity makes them a great long-term investment for a nano planted setup.

What Makes Them Stand Out

A school of 12–15 chili rasboras in a planted tank is a stunning sight. They swim in tight formation, creating a darting cloud of red against dense green plants. No other nano fish delivers that visual impact at this size.

They also pair beautifully with freshwater shrimp. The bold red bodies contrast sharply with blue velvet or yellow neocaridina shrimp. This combination is one of the most popular aquascape displays among nano keepers in 2026.

Setting Up the Perfect Chili Rasbora Tank

Chili rasboras need a heavily planted, dimly lit tank that mimics their native Bornean blackwater habitat — bright, bare setups stress them out and wash out their color. The closer the tank resembles a peat swamp, the healthier and more vivid the fish will be.

A 5-gallon tank works for a group of 6–8 fish. For a school of 10 or more, use a 10-gallon or larger. More water volume means easier chemistry stability and better schooling.

Plants and Hardscape

Best plants and decor for a chili rasbora setup:

• Java moss and Christmas moss — perfect for egg scattering and cover
• Floating plants (frogbit, dwarf water lettuce) — reduce light naturally
• Stem plants (ludwigia, rotala) — add depth and color contrast
• Driftwood — releases tannins, gently softens and acidifies water
• Indian almond leaves — reduce stress, soften water, add a natural floor layer

Leaf litter on the substrate is a great addition. It replicates the forest floor of their native Borneo streams. Chili rasboras spend significant time near the bottom, so a natural substrate layer matters.

Substrate and Filtration

Use dark, fine-grained substrate. It makes their red coloring pop against the background. A light substrate makes the fish look pale and washed out.

For filtration, use a sponge filter or a low-flow hang-on-back filter with a baffle. Chili rasboras are tiny and weak swimmers — strong current exhausts them fast. Target a gentle 3–5x tank volume turnover per hour.

Pro Tip: Add a few drops of blackwater aquarium extract to replicate tannin-stained water. It lowers pH gently, reduces stress, and brings out bolder red coloring — all in one step.

Chili Rasbora Water Parameters

Getting water chemistry right is the most critical step in chili rasbora care — these fish are sensitive to hard, alkaline water and will not thrive without soft, acidic conditions. They evolved in peat swamps with minimal dissolved minerals and naturally dark, tannin-stained water.

Target these parameters:

If your tap water is above pH 7.5 or GH 15+, use RO water or a tap/RO blend. Hard, alkaline tap water stresses chili rasboras and shortens their lifespan over months of exposure [2].

Cycling and Water Testing

Always fully cycle the tank before adding chili rasboras [2]. They're far more sensitive than hardy fish like guppies or danios. An ammonia spike in an uncycled tank can wipe out an entire school within days.

Test water weekly with a reliable kit like API Freshwater Master Test Kit. Track pH, ammonia, nitrite, and nitrate together. Stable readings matter more than hitting any single exact target.

Pro Tip: Do 20–30% water changes weekly. Small, frequent changes keep chemistry far more stable than one large monthly change. Always match temperature and pH of new water before adding it.

Common Myth: "Chili rasboras need pH below 5.0 to survive." Reality: Keeper-reported data consistently shows healthy, breeding fish at pH 5.5–6.8 in captivity [2]. Stable, soft water is the real goal — extreme acidity isn't necessary.

What to Feed Chili Rasboras

Chili rasboras are micro predators with tiny mouths — standard fish food is too large, and they need live or frozen micro foods to truly thrive. Dry flakes fed exclusively lead to poor color and a shortened lifespan.

Best foods for chili rasboras:

• Baby brine shrimp — protein-rich, easy to hatch at home
• Micro worms — cheap to culture, great for daily feeding
• Daphnia — stimulates natural foraging behavior
• Cyclops — nutrient-dense micro crustaceans
• Vinegar eels — ideal for fry and small adults
• Crushed high-quality flake — fine powder only, as a weekly supplement

Feed 2–3 small meals per day. Remove uneaten food within 2–3 hours. In a nano tank, leftover food rots quickly and spikes ammonia.

Feeding Tips for Nano Tanks

Overfeeding is the number one water quality killer in small tanks. In a 5-gallon setup, even a few extra pinches of food can cause an overnight ammonia spike. Feed only what the fish eat in under 2 minutes.

A floating feeding ring keeps food contained in one spot. It prevents food from drifting to the substrate and decomposing unnoticed.

See our top picks for live nano fish foods on Amazon to stock up on the best micro foods for chili rasboras.

Pro Tip: Culture microworms in a small deli container with oatmeal and a pinch of yeast. They're ready in 5–7 days and provide a free, continuous live food source with minimal upkeep.

Best Tank Mates for Chili Rasboras

Chili rasboras need very small, calm tank mates — any fish over 1.5 inches will stress, out-compete, or eat them. Even gentle community fish like neon tetras are too large and fast to share a tank comfortably.

As of May 2026, the keeper community consensus is to keep chili rasboras with invertebrates and micro fish only. This protects them from food competition and reduces chronic stress.

Good Tank Mates

These species pair well with chili rasboras:

• Pygmy corydoras — similar size, peaceful bottom dwellers
• Otocinclus catfish — algae cleaners, won't bother rasboras
• Sparkling gourami — shares blackwater water preferences
• Celestial pearl danios — similar size and temperament
• Neocaridina shrimp (cherry, yellow, blue velvet) — colorful, completely safe
• Caridina shrimp — compatible in soft, acidic water
• Nerite and mystery snails — helpful algae cleaners, no threat

Tank Mates to Avoid

Keep chili rasboras away from:

• Any fish larger than 1.5 inches
• Bettas — even calm ones may attack bright micro fish
• Dwarf cichlids (German blue rams, apistogramma species)
• Fast, nippy fish (tiger barbs, serpae tetras)
• Large loaches or any pleco species

According to Seriously Fish, chili rasboras do best in species-specific or carefully curated micro-fish communities. Mixing them with larger fish — even gentle ones — often leads to chronic stress and a noticeably shorter lifespan.

Breeding Chili Rasboras in a Home Tank

Chili rasboras breed readily in a well-conditioned planted tank — no separate breeding setup required. They scatter eggs on fine-leaved plants like java moss, and adults rarely eat fry in a densely planted environment.

Breeding happens naturally when water conditions are stable and live food is plentiful. A good planted community tank will often produce fry without any deliberate effort.

How to Trigger Spawning

Follow these steps to encourage breeding:

1. Lower pH to 5.5–6.0 using tannins or a tap/RO water blend
2. Raise temperature slightly to 78–80°F
3. Feed live foods (baby brine shrimp, daphnia) daily for 1–2 weeks
4. Add dense moss — java moss or Christmas moss works best
5. Dim the lights to simulate overcast forest stream conditions

Males intensify in color during courtship and chase females through the moss. Spawning usually occurs in early morning near floating plants or moss mats.

Raising Fry Successfully

Eggs hatch in 24–36 hours. Fry are extremely tiny — barely visible to the naked eye at first [3]. They need infusoria or vinegar eels for the first 5–7 days.

After the first week, fry accept micro worms and freshly hatched brine shrimp. According to Practical Fishkeeping, a heavily planted tank with established microfauna can raise chili rasbora fry to adulthood with minimal keeper intervention [3].

Common Myth: "You must remove adult chili rasboras after spawning or they'll eat the eggs." Reality: In densely planted tanks, adults rarely prey on eggs or fry. Keeper-reported colony breeding is well-documented — dense plant cover protects the young effectively.

Common Mistakes New Keepers Make

Avoid these six errors to keep your chili rasboras healthy long-term:

1. Keeping too few fish. Groups under 8 are stressed and hide constantly. Keep at least 10 for natural behavior and peak color.

2. Using untreated hard tap water. Hard, alkaline water shortens lifespan and fades color over time. Condition water or blend with RO.

3. Feeding only dry flakes. Flakes alone cause dull coloring and poor health. Rotate live and frozen micro foods into the weekly feeding schedule.

4. Using a powerful filter. Strong filters create current that exhausts tiny fish. Always use a sponge filter or baffled HOB filter.

5. Adding fish before cycling is complete. Chili rasboras won't survive ammonia spikes. Cycle to 0 ppm ammonia and nitrite before adding any fish.

6. Pairing with larger tank mates. Even gentle larger fish out-compete chili rasboras for food and cause stress. Stick to micro fish and invertebrates only.

Chili Rasbora vs. Similar Nano Fish

Best pick: Choose chili rasboras for maximum color impact in a blackwater nano setup. Choose ember tetras for an easier, more beginner-friendly option.

Ready to get started? Shop now for the best nano aquarium planted tank kits on Amazon and start building your chili rasbora setup today.