Chili Rasbora – Size, Tank Mates, And Care Guide

The Chili rasbora (Boraras brigittae) is sometimes also called the Mosquito rasbora. These brightly colored, tiny fish only grow to measure around half an inch in length, making them one of the smallest tropical aquarium fish you can buy.

Chili rasboras are active yet peaceful little characters, thriving in a community tank of other small, non-aggressive tank mates or a single-species setup when kept in a large school. These charming nano fishes are relatively easy to care for, but they can be very sensitive to water quality, so they’re not the ideal choice for a beginner.

In this comprehensive guide, we tell you everything you need to know about looking after the glittering swimming jewel called the Chili rasbora. 

Chili Rasbora – Overview

Origins

The Chili rasbora was first described in 1978 by Dieter Vogt, who named the fish Rasbora urophthalma brigittae in honor of his wife, Brigitte. The fish’s natural habitat is teeming with mosquitos, hence the creature’s other common name, Mosquito rasbora.

Interestingly, “Boraras” is an anagram of the fishes’ generic name “rasbora,” which refers to the reversed ratio of caudal and abdominal vertebrae in this fish genus.

Chili rasboras belong to the Actinopterygii class of ray-finned fishes and are characterized by the bony rays that support their fins. Within that class is the Characiformes order, a subgroup of ray-finned fish that contains 17 families, as well as characins. There are six recognized species of rasboras, including the Chili rasbora.

Natural Habitat

The Chili rasbora comes from Southwestern Borneo and the Indonesian provinces of Kalimantan Tengah, and Kalimantan Selatan.

The fishes’ natural habitat consists of blackwater pools and streams, where the flow is very slow, and the peat-stained waters are extremely low in minerals and salts. The water pH here can be as low as 4.0.

The water is dark and dim, and the fish also enjoy plenty of hiding places and cover that’s provided by fallen leaves, submerged branches and roots, and aquatic vegetation. The habitat is very sheltered and is shaded by overhanging trees and shoreline plants.

At the time of writing, the Chili rasbora is not listed on the IUCN Red List. However, much of the fishes’ natural habitat is rapidly declining, so the species’ future in nature is by no means assured.

Appearance

Chili rasboras may be tiny, but their brilliant coloration makes up for their diminutive size. A shoal of these fishes schooling together or darting amid dense planting is a stunning sight, which makes the species a favorite of many hobbyists.

The fish’s body is an intense red in color with a dark stripe and small darker spots at the base of the caudal and anal fins. The edge of the dark striped marking is highlighted by a brilliant crimson band.

The anal and dorsal fins have dark markings along the anterior perimeter with brilliant red highlighting in male specimens. During the breeding season, male Chili rasboras have intense crimson markings on their caudal and pelvic fins.

Size

Chili rasboras are tiny fishes, reaching only around half an inch long at full maturity.

Life Expectancy

Chili rasboras have a life expectancy of six to eight years if properly cared for.

Activity Level/Temperament

Chili rasboras are active fish, spending much of their time schooling together in the aquarium’s midwater area. Generally, if you keep groups of these fishes, they will be more confident, whereas if you only have a couple of rasboras, they will tend to hide among your plants.

Compatibility And Tankmates

The Chili rasbora is a peaceful, timid fish, which makes them a good choice for a community setup, provided that you don’t have any very large, aggressive species that might try to make a meal out of the tiny rasboras. Basically, any species that won’t try to eat the rasboras and enjoys soft, acidic water with a low flow rate is a pretty good bet.

Ideally, you want to choose tank mates that are also small, shy, and non-aggressive. Some good examples of suitable species include neon tetras, small catfish, gouramis, dwarf cichlids, minors, and other rasboras.

Invertebrates are also a great choice of tankmates for Chili rasboras. Dwarf shrimp and aquatic snails can help keep algae down and make an attractive, interesting addition. Check out Cherry shrimp, Amano shrimp, and Mystery snails, which all make suitable tankmates for your rasboras.

Single-species Option

If you have a small nano tank, you might want to consider keeping a school of eight to ten Chili rasboras. These are naturally schooling fish that should always be kept in largish groups, and they do make a wonderful sight when kept in a single-species setup.

Fish Species to Avoid

As previously mentioned, larger, aggressive fish such as bettas and angelfish should be avoided. Although they may not harm the rasboras, bossy fishes will chase and harass their smaller tankmates. That causes stress to both parties, leading to a compromised immune system and potential health problems.

Feeding

Chili rasboras are pretty straightforward to feed. These fish are essentially omnivorous, meaning that they need a diet containing a mixture of vegetable and plant matter and meaty protein.

The main challenge to feeding your Chili rasboras is finding foods that are small enough to fit into the fish’s tiny mouths!

What To Feed Your Chili Rasboras

So, when choosing food for your rasboras, think about what you would feed to tiny fry and go with that. Live foods are a great option, especially small daphnia, baby brine shrimp, micro-worms, wingless fruit flies, vinegar eels, mosquito larvae, and small bloodworms.

Frozen foods are an option if you can’t get hold of live food. However, you will need to thaw the food and chop or mince it into pieces that are small enough for the rasboras to eat.

Dried fish foods are much easier to feed to your rasboras, although they don’t have the same nutritional value as live foods. Make sure that you choose a high-quality fish flake or pellet food, and crumble it into a powder. You can also feed golden pearls, crushed freeze-dried daphnia, and brine shrimp eggs.

What Size Foods?

To give you an idea of the size of the food you want to feed your Chili rasboras:

• Foods in the 100 to 150-micron size range are suitable for small fry.
• Foods under 500-microns are fine for small adult fish.
• Foods under 800-microns are fine for full-grown adult fish.

How Much and How Often to Feed

I recommend that you feed your fish twice a day.

Rather than offering your rasboras one large meal, it’s better for the fishes’ digestion to feed them little and often. So, two small meals are the way to go.

If you’re not around during the daytime or evening to feed your fish, you might want to consider using an automatic fish feeder with a timer that you can set to deliver a small portion of food at a preset time. These devices are relatively inexpensive and can provide the ideal solution for busy aquarists.

Tank Requirements

Chili rasboras are relatively easy to care for, as long as you provide them with the correct water conditions.

Tank Size

Thanks to its tiny size, the Chili rasbora is ideal for small, nano tanks. So, essentially, you can keep these fishes comfortably in a 5-gallon tank.

And when you consider that the general rule of thumb for fish numbers is one inch of fish per one gallon of water, you can see that you can have a school of ten rasboras in a 5-gallon nano aquarium.

However, even though the rasbora is a tiny fish, overcrowding will still cause water quality problems and overburden your filtration system. So, for that reason, be careful that you don’t cram too many fish into your tank.

Tank Setup

As with any fish species, your livestock will thrive if you provide them with an aquarium environment that closely replicates their wild habitat.

Substrate

A dark-colored substrate will really make your Chili rasboras intense colors pop! These fish don’t burrow or forage through the substrate, so fine gravel or sand that mimics the river bottom of the rasbora’s natural environment is a good choice.

The substrate in blackwater habitats typically has a layer of fallen leaves scattered across it, and you can replicate that in your home tank by adding a few handfuls of dried almond leaves. Decomposing leaves leech tannins into the water, staining it the color of tea, and they can also help to lower the water pH, which is perfect for Chili rasboras.

Decorations

Again, to imitate the rasboras’ natural home, you’ll need to include lots of lush planting that the fish can use for cover, together with driftwood, twisted roots, rockwork, and caves.

Leave plenty of space in the middle of the water column where the fish can school together.

Habitat Requirements

Filtration

In nature, the Chili rasbora inhabits pools and rivers where the water movement is slow or moderate. If your mechanical filter generates too much current, these little fish will struggle to swim against the flow.

I recommend that you use a simple sponge filter that provides a small amount of movement at the water surface. If necessary, use decorations and plants to buffer the flow.

Water Parameters

When it comes to water parameters, that’s an area where many beginners have problems when they take on Chili rasboras. These fish come from an environment with very specific water conditions. You need to mimic these closely in the aquarium if the rasboras are to remain healthy and thriving.

Water Temperature

Chili rasboras are tropical fish that need a water temperature of between 68° to 83° Fahrenheit.  

Water Hardness and pH Range

The blackwater habitat that’s home to Chili rasboras has extremely soft water containing very few minerals or salts. So, for the fish to remain healthy in the aquarium, the water hardness should be between 1 and 10 dKH, and the pH range should be from 4.0 to 7.0.

Lighting

The rivers and pools in which Chili rasboras live are found in densely forested areas and are shaded by the overhanging tree canopy and dense shoreline vegetation.

You can dim your lighting in the aquarium by using floating plants to diffuse the light and provide shelter and cover for the fish. If you prefer, you can choose a lighting unit that allows you to alter the light you have in your tank. If you take that route, there are plenty of beautiful low-light plant species to grow that do very well under dim lighting.

Tank Maintenance

Once you have the water conditions and tank environment set up correctly, Chili rasboras are pretty easy to care for. That said, you do need to give your fish a clean tank with well-oxygenated water.

The most important thing for rasboras is that the water parameters remain stable and constant, as any sudden fluctuations in the water chemistry are likely to see mass die-offs.

Vacuum the Substrate

Each week you need to use an aquarium vacuum cleaner to remove uneaten fish food, fish waste, and decaying plant matter from the substrate and the areas where waste tends to accumulate, such as underneath decorations, around plant bases, and beneath your box filter if you have one. If you neglect that task, the ammonia that the decomposing organic waste produces will make the water toxic to your fish.

As part of your general maintenance regimen, you should trim away dead plant leaves and overgrowth, and refresh dried leaf litter as required.

Carry Out Partial Water Changes

As well as vacuuming the tank, you should carry out 10% to 15% weekly partial water changes so that ammonia, nitrate, and nitrates remain at acceptable levels. Ideally, there should be no more than 20ppm nitrates in the water, while ammonia and nitrites should be zero.

Maintain Filter Cartridges/Filter Media

Filter cartridges should be replaced periodically as per the manufacturer’s guidelines, and you’ll also need to rinse your filter media in tank water to get rid of the sludge that will otherwise prevent the flow of water through the media.

Setting Up the Aquarium

First of all, gather together everything that you need for your fish tank:

• Dark gravel substrate
• Dried almond leaves
• Lighting unit
• Filtration system
• Heater
• Aquarium thermometer
• Decorations
• Plants

How to set up your aquarium:

1. Begin by rinsing your aquarium substrate under running water to remove any dust and loose debris.
2. Once the water runs away clear, you can add the gravel to your aquarium to a depth of two or three inches, and scatter a couple of handfuls of dried almond leaves across the substrate to create a blackwater environment.
3. Set up and install your filtration unit and heater, but don’t turn them on yet.
4. Now, you can fill your tank with unconditioned tap water. For your biological filtration system to kick off the nitrogen cycle, don’t condition the tap water. Tap water contains ammonia that the bacteria in the filter media need to start the cycle before you introduce your fish.
5. To avoid displacing the gravel all over the bottom of the aquarium, place an upturned dish on top of the substrate, and pour the water over it.
6. Rinse your tank decorations to get rid of any dust, and add them to your aquarium.
7. Remove dead leaves and broken stems from live plants before planting them in your aquarium. Remember to allow plenty of space between specimens so that the plants can grow and spread.
8. Turn on your filtration system and heater, and leave the aquarium to cycle for at least ten days before you add your Chili rasboras and other livestock. I recommend that you test the aquarium water to ensure that the levels of ammonia and nitrites are at zero before you go out and buy your fish.
   
   If you put fish into a tank that’s not fully cycled, your new pets will probably not last more than a few days before they succumb to the effects of ammonia poisoning.

Health and Disease

Chilli rasboras are actually pretty hardy fish, as long as you keep the water parameters stable and constant.

Signs of Good Health

Chili rasboras are generally lively fishes that love to school in the tank’s midwater area or dart in and out of the plants and tank decorations.

Red Flags

Red flags that could indicate that health problems may be brewing include:

• Not eating
• Inactivity
• Hanging at the water surface
• Swellings and ulcers
• Flicking against tank decorations and the substrate

Common Health Issues And Treatment

 

Breeding

Chili rasboras are very easy to breed in the home tank, as they tend to ignore their eggs and won’t eat them as some fish species do. Although you can set up a separate breeding tank, there’s a good chance you will end up with some fry in your display aquarium, as long as it’s densely planted so that any surviving fry has somewhere to hide.

If you have a shoal of eight to ten rasboras, you’re sure to have a mixture of males and females, and spawning takes place almost constantly once the fish are mature. Once the eggs are laid, they fall to the bottom of the tank, hatching within 36 to 72 hours. After 36 to 48 hours, the fry becomes free-swimming.

Feed the minute fry on infusoria and commercial fry food until they are large enough to take tiny baby brine shrimp and the like. The fry will be mature enough to breed once they reach six months of age.

Availability

Chili rasboras are not commonly seen in fish stores, but you can find them online, typically for a couple of dollars per fish. 

Product Recommendations

• Fish tank (minimum size 5 gallons)
• Filtration system
• Heater
• Aquarium thermometer
• Water conditioner
• Lighting unit
• High-quality tropical flake food
• Selection of frozen foods
• Dark gravel substrate
• Rocks, driftwood, twisted roots, dried almond leaves
• Books on keeping tropical fish
• A fishnet
• Aquarium vacuum
• Algae magnet

In Conclusion

I hope you enjoyed our guide to caring for the Chili rasbora.

If you successfully keep rasboras, tell us all about your setup in the comments box below. And, don’t forget to share our article with your fellow hobbyists if you found our guide to keeping these gorgeous little fishes helpful!