Chili Rasboras – Detailed Guide: Care, Diet, and Breeding

Chili Rasboras (Boraras brigittae) – Detailed Guide Care, Diet, and Breeding

Boraras brigittae, commonly known as Chili Rasboras, is one of the smallest fish in its family boasting stunningly vibrant colors. It is excellent for keeping in aquascapes (such as Iwagumi) and nano aquariums.

Despite its size, Chili Rasboras are quite hardy fish, provided that the first month of adaptation has been successful.

If you are interested in keeping Boraras brigittae or want to learn more about this species, this care guide will tell you everything you need to know, including their behavior, feeding preferences, ideal tank setups, and how to care for them.

Quick Notes about Chili Rasboras

Name Chili Rasboras
Other Names Micro Rasboras, Micro fish, Mosquito danios, or Rasbora Mosquito
Scientific Name Boraras brigittae
Water type Freshwater
Tank size (optimal) 10 gallons (~40 liters)
Keeping Easy-Medium
Breeding Difficult
Size 0.6 – 0.8 inches (1.5 – 2 cm)
Optimal Temperature 72 – 82°F (22 – 28°C)
Optimal PH 5.0 – 7.0 
Optimal GH 1 – 8
Dwellers top to mid-dwelling
Nitrate Less than 40
Diet Detritivorous
Temperament Peaceful
Life span 4-8 years
Color Form Red

Taxonomy of Chili Rasboras

In 1978, German ichthyologist and aquarist Dieter Vogt (1927 – 2020) described this fish as Rasbora urophthalma brigittae. Nowadays the correct name is Boraras brigittae.

Kingdom: Animalia (Animals)
Phylum: Chordata (Vertebrates)
Class: Actinopterygii (Ray-finned fishes)
Order: Cypriniformes (Carps, minnows)
Family: Cyprinidae (Carp family)
Genus: Boraras (Small fish)
Species: B. brigittae

The findings show that Boraras species belong to a single evolutionary lineage, which is identified by 4 distinct characteristics:

  1. they don’t have a particular type of canal near their eye,
  2. their urohyal bone has a unique shape,
  3. their fourth rib on the side of their body is elongated, and
  4. a specific bone called the postcleithrum is attached high up on another bone called the cleithrum.

Etymology

This genus name “Boraras” is an Indian word for a fish, also used in Malay peninsula. Additionally,  “Boraras” is an anagram of the generic name “Rasbora,” symbolizing the reversed ratio of abdominal and caudal vertebrae unique to this genus.

This species was named “Brigittae” in honor of Dieter Vogt’s wife, Brigittae.

Distribution of Chili Rasboras

Chili Rasboras (Boraras brigittae) – Detailed Guide Care, Diet, and Breeding destributionBoraras brigittae is endemic to Indonesia (from West Kalimantan and some parts of Central Kalimantan). Its range extends from southwestern Borneo to the Jelai Bila river basin near the town of Sukamara.

Habitat of Chili Rasboras

In their natural habitat, Chili Rasboras usually occur in tranquil stagnant pools, ditches, swamps, and slow-flowing streams.

Typically, they inhabit areas with muddy substrate and dense vegetation. The water often takes on a dark brown hue due to tannins and other substances released during the decomposition of organic matter such as fallen leaves, branches, and driftwood.

Description of Chili Rasboras

Chili Rasboras (Boraras brigittae) – Detailed Guide Care, Diet, and Breeding profile

  • Size. This is a very small freshwater fish. The typical adult size of this species ranges from 6 to 0.8 inches (1.5 to 2 cm) in length.
  • Body Shape: The body is slender, elongated, and laterally compressed. The body shape is somewhat streamlined, typical of Rasboras.
  • Coloration. The main body coloration is red or pinkish with prominent black stripes along the sides and a slight thickening in the center. This line terminates with a black wedge-shaped spot at the beginning of the caudal fin. A red stripe runs along its upper body, extending to the base of the tail.
    Note: The fish displays muted colors when young. However, its hues become more vibrant around 1 year old.
  • Fins. The fins are small, semi-transparent, and may have red and black streaks. There is a small dark spot at the base of the tail. Red spots adorn the caudal fin, while sections of the dorsal and anal fins also display red coloration.

Lifespan of Chili Rasboras

Currently, there is no data available on the maximum lifespan of Boraras brigittae in the wild.

In aquariums, with appropriate conditions, Chili Rasboras can live for around 4 to 8 years.

Typical Behavior of Chili Rasboras

Temper:

Chili Rasboras are absolutely peaceful fish. They will not bother anybody in the community tank. These fish do not exhibit aggressive behavior to other species of fish.

Although males of this species will compete for dominance with each other and dominant male may even claim some territory for that.

Anyway, despite the existence of hierarchy, all conflicts are usually resolved without causing any harm. Their “Fights” look like this: facing another males head-on or head-to-tail, they begin to “lash out” with their fins and bodies towards each other, intensifying their colors in the process.

They do not nip.

Sociality:

Chili Rasboras (Boraras brigittae) – Detailed Guide Care, Diet, and Breeding - shoalingAlthough Chili Rasboras is a social species, they do not stay in close proximity all the time. Thus, it is not schooling but rather a shoaling fish.

In the aquarium, it is recommended to start with a group of at least 6-8 individuals. Larger groups contribute to their overall happiness and reduce stress levels.

Activity:

Chili Rasboras are moderately active fish. Generally, they do not swim like crazy in aquariums but they can move really swiftly when they choose to.

This small fish is not very skittish. On the contrary, it will swim quite actively even in open areas. Of course, it may need some time to adapt to its surroundings.

Additionally, you may even notice that when first introduced, the fish pales, which is quite normal. Once the stress subsides, its color will return. This process usually takes from a couple of hours to several days.

Interestingly, their jumping ability, particularly when stressed or frightened, is often overlooked in other sources and articles.

Placement in Tank:

Generally, they spend most of their time at the top and middle parts of the tank.

They enjoy exploring their environment and are particularly fond of areas with tall and dense vegetation or places to hide.

Features:

  • Social: Yes
  • Activity: Moderate
  • Placement: Top and middle dwellers
  • Peaceful: Yes
  • Nippers: No
  • Jumpers: Yes

Diet of Chili Rasboras

Boraras brigittae is a diurnal omnivore. In nature, these fish feed on microscopic organisms, including insect larvae in densely vegetated areas.

They are not very picky eaters. In the aquarium, Chili Rasboras can be provided with a diverse range of frozen or live foods, including:

Generally, they will happily consume dry and freeze-dried foods such as flakes, pellets, and crisps as long as it is small enough to fit into their mouth for mastication and digestion. Therefore, large pieces of pills, granules, and flakes food should be crumbled into tiny parts (like powder).

Note: Chili Rasboras go crazy for live baby brine and fluval bug bites! They absolutely love it. It also helps their coloration!

How to feed Chili Rasboras:

This is a diurnal species, so it is better to feed them in the morning.

Ideally, feed them in small portions (at least 2 times a day) rather than a large amount once a day. This mimics their natural feeding behavior and helps prevent overfeeding and digestive issues.

Tip: When feeding, it’s better to choose foods that will stay on the surface longer and slowly sink, as Chili Rasboras don’t often pick up food from the bottom.

Features:

  • Diet Type: Omnivore
  • Food Preference: Meat
  • Feeding Frequency: Daily

Are Chili Rasboras Plants Safe?

Yes, this species can be kept in planted tanks. They will not eat any healthy plants in the tank. This species does not eat living plant material.

Keeping and Housing Chili Rasboras

Before introducing them to your tank, it is important to create optimal environment for them. Therefore, ensure your tank is properly cycled. Regularly test water using a kit to monitor ideal conditions.

Tank size:

Chili Rasboras are small fish and do not require a lot of volume. They can be easily housed even in a 5-gallon (20-liter) nano-tank.

Ideally, a 10-gallon tank (40 liters) will suit them way better. This volume will be enough even for 15 – 20 fish. They do not produce a lot of waste, so as long as you have a good filtration, it is possible to have even more.

In larger tanks, they will be ‘lost’ and difficult to see. However, the challenge with nano tanks is maintaining stable water parameters, which can be quite difficult for beginners.

Therefore, unless you are already an experienced aquarist, I would recommend staying away from small setups.

Important: Do not forget that Chili Rasboras is jumpers! So, it is imperative to take measures: use a tight-fitting lid, lower the water level, use floating plants, etc.

Water parameters:

Chili Rasboras inhabit blackwaters in the wild. This discoloration is primarily due to the presence of tannins and other organic compounds leaching into the water from decaying plant matter, such as leaves, branches, peat, etc.

That is why these fish clearly prefer biotopes with very soft water and acidic conditions.

Note: To create the effect of tropical “blackwater,” we can use, for example, Tetra ToruMin solution with natural peat extract.

Temperature: Ideally, Chili Rasboras need water temperatures ranging between 72 to 82°F (22 to 28°C). They tolerate cooler temperatures (up to 68°F or 20°C) in winter if acclimated slowly.

pH: The ideal pH range is between 5.0 – 7.0. In their natural environment, they thrive in acidic waters.

Hardness: The tank should preferably have soft to medium water hardness as well. Therefore, anything in the range of 1 – 8 GH is acceptable. They do not like very hard water.
Note: Although they can adapt even to harder water, eventually, it will reduce their lifespan.

Lighting:

Chili Rasboras does not like bright light, it makes them stressed. These fish enjoy subdued lighting.

Therefore, if you are creating an aquarium specifically for this species, you should consider only plants that can thrive in low lighting conditions, as well as floating plants, which will help create dim lighting in the aquarium.

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Water flow:

In the natural ecosystem, Chili Rasboras inhabit shallow waters where the current is absent or very slow-moving. They are not strong swimmers.

Therefore, stagnant water or very slow water currents are recommended for tanks housing this species.

Filtration:

Filtration will be crucial as it partly affects the water flow in the aquarium. Therefore, it is recommended to choose filters with minimal flow, such as sponge filtration.

Important: Another issue is that Chili Rasboras can get sucked into the filter. Therefore, if you are using filters like Hang on Back Filters, it’s best to use an extra pre-filter in the form of a sponge to prevent fish from being sucked in.

Substrate:

No special requirements.

In planted tanks you can use an active substrate, besides boosting plants’ growth rate it will also help you to maintain a low pH level in the water.

Tip: Although you can choose any substrate for the tank, it is better to have a dark color so that the fish looks more contrasting against its background.

Decorations:

Chili Rasboras (Boraras brigittae) – Detailed Guide Care, Diet, and BreedingChili Rasboras lives in its natural habitat, which is characterized by an abundance of driftwood, leaf litter, and vegetation. They like to hide darting in and out of cover.

This should be replicated in an aquarium.

Plants provide good hiding spots as well. You can use floating plantsfake plantsdriftwoodleaves, and rocks to provide great hiding spots for them.

Related article:

Acclimation:

Before putting Chili Rasboras into the tank, you need to acclimate them properly.

Do not rush the process!  

Be very careful during the acclimation process and use the drip method. Sudden changes in habitat can harm them.

Tip: I would also recommend turning off or dimming the lights when you add them to the aquarium. This will reduce their stress and help them to settle down more quickly.

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Problems Associated with Chili Rasboras

Despite being very small fish, Chili Rasboras are quite resilient and hardy. Usually, there are no problems with them except during the first month!

The thing is, most of these fish sold are captured in the wild. As a result, they undergo stress from prolonged transportation, and there is also a risk that they may be infected with something. All of this manifests in the first month, which is the most challenging.

Internal parasites

They start to develop sunken stomachs and become noticeably thinner. They seem to lose their energy, hiding away and showing signs of apathy. Strangely, their coloration often remains normal, and their scales are in perfect condition.

Treatment: Use Metronidazol – 1g/100liters and do water changes 40% for the next 2 days.

Columnaris

Columnaris is a bacterial infection that affects fish, often appearing as white, fuzzy patches on their skin, fins, or mouth (mold-like lesions). It’s highly contagious and can spread rapidly throughout the tank, particularly in stressed or weakened fish.

Treatment: Use Seachem Kanaplex for 1 week. Do 30-40% water changes at the 3rd and 5th day.

Ich

Ich is a common parasitic infection that affects freshwater aquarium fish. It appears as tiny white spots, resembling grains of salt, on the fish’s body, fins, and gills. It is highly contagious.

Treatment: Increase the temperature of the aquarium to around 82-86°F (28-30°C). Higher temperatures accelerate the life cycle of the Ich parasite, making it more susceptible to treatment. Dose Ich-X, using 5 ml of medication per 10 gallons of aquarium water, and allow 24 hours for the treatment to take effect. Do water change and dose again.

Important: Quarantine Infected Fish. Remove it from the main tank and place them in a separate quarantine tank to prevent the spread of deseases.

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Breeding Chili Rasboras

Unfortunately, the reproductive process of Boraras brigittae is practically unexplored in scientific literature.

Some articles suggest that breeding them is not particularly difficult. In well-established, mature aquariums, a small number of fry may start appearing without human intervention. In reality, this is not the case.

Breeding them in aquariums has proven to be a challenge as well.

According to the scarce information:

  • Boraras brigittae is an egg-scattering spawner.
  • They become sexually mature at the age of 8-10 months.
  • These fish are daily spawners. Females lay only 2-3 eggs each day.
  • Начало формы
  • Parents do not care for their eggs and/or fry.
  • Sexual dimorphism is weak. Females are slightly larger and having a rounder belly. Males have more vivid coloration compared to females.
  • Egg incubation last from 24 to 48 hours.
  • After hatching, fry rely on the egg sack as a nutritional reserve in the first days of life.
  • After 4-5 days, the fry already start attempting to swim, and adopt a horizontal position. From this point on, the fry spend most of their time swimming and often hide among plants. At this stage, they are almost entirely transparent.
  • After 5-7 days they can eat microwormsvinegar eelsrotifers, and brine shrimp.
  • They become more or less similar to adults after 1.5-2 months, although they usually attain their full coloration only by their first year of life.

Rearing Tank (Inducing spawning)

  • Temperature: 79 – 82°F (26 – 28°C),
  • pH: 5.0 – 6.5,
  • hardness: 1 – 6 GH,
  • dim lighting,
  • a protective net is placed on the bottom of the spawning tank or spawning mop,
  • no substrate (to easier find and collect eggs),
  • add driftwood, almond leaves, boiled alder cones and/or blackwater conditioners for the tannins and softening of the water. You can also add rainwater or RO water,
  • reduce the strength of water flowing,
  • use an extra pre-filter to prevent fry from being sucked in.

Select 2-3 pairs of breeders for spawning. Condition parents by giving lots of live food such as cyclops, brine shrimp, and artemia for several weeks.

Important: After spawning, remove the parents from the tank to prevent them from eating the eggs and fry.

Chili Rasboras and Suitable Tankmates

This is a very friendly fish that is suitable even for nano tanks. 

When choosing tankmates for Chili Rasboras, it is important to consider their size and behavior. They cannot compete with other species and might be targeted for bullying.

Fish:

You can keep this fish with other peaceful fish of similar size. You won’t achieve success if you keep them with larger or aggressive fish; they will spend all their time hiding among plants.

Ideally, you need to choose species that prefer (or can tolerate) soft and slightly acidic aquarium water, such as:

Shrimp:

These small fish will be a great addition to a shrimp tank. Chili Rasboras will not harm adult or juvenile dwarf shrimp that are a couple of weeks old.

They are not active hunters, and considering that they mostly inhabit the upper and middle layers of the tank, it reduces their chances of encountering shrimp fry.

Therefore, they are often considered excellent tank mates for shrimp. Keeping these fish with shrimp has shown that the shrimp population continues to increase regardless.

However, if you plan to keep and breed very expensive shrimp, then undoubtedly, even Chili Rasboras should be excluded from the aquarium, as newly hatched shrimp can be eaten. You do not want that.

Snails:

Chili Rasboras is compatible with any freshwater snail. They do not eat or harass them.

Avoid:

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In Conclusion

Chili Rasboras is a fascinating and beautiful aquarium fish. Once establish in the tank, they are easy to care for, making it suitable for beginners.

They are very peaceful and can coexist with various fish species in similar conditions. It’s a great addition to community aquariums.

The main problem though, in my opinion, is that breeding them in captivity is quite difficult.

References:

  1. Conway, Kevin W. “Monophyly of the genus Boraras (Teleostei: Cyprinidae).” Ichthyological Exploration of Freshwaters16, no. 3 (2005): 249.
  2. Körner, H.-J., 2010- BSSW-Report 22(2): 21-28 Boraras merah ist doch ein Synonym von Boraras brigittae!
  3. Liao, T. Y., Kullander, S. O. and F. Fang, 2009- Zoologica Scripta 39(2): 155-176 Phylogenetic analysis of the genus Rasbora (Teleostei: Cyprinidae).

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