The Chili Rasbora (scientific name Boraras brigittae) is just a gorgeous nano fish that swims and plays happily in schools. Not only are they attractive fish, but they have stellar personalities. They really have all the positives in a tiny package. Native to Indonesia’s Southwestern Borneo, Chili Rasbora, also known as the Mosquito Rasbora, is one of the smallest tropical fish found in home aquariums. The males are known for their bright ruby red color (when they are properly cared for).
Originally described by Dieter Vogt in 1973, the Chili Rasbora is named Rasbora brigittae after Dieter’s wife, Brigitte. The Chili Rasbora is not a true Rasbora and in 1993 was put in the Boraras genus. The alter ego moniker Mosquito Rasbora comes from the Chili Rasbora’s natural habitat, which is loaded with mosquitos. Although there are a number of Boraras species that are popular in the aquarium trade, Chili Rasboras are the favorite of hobbyists because they are so beautiful to look at.
Occupying the top and middle of the aquarium water column, Chili Rasbora is easy to spot despite its small size. And although they prefer the top and middle, don’t be surprised if you see them swimming and eating at the middle and bottom levels. When they get together as a school, they are unpredictable, yet never boring to watch. They are very peaceful fish and get along with other peaceful fish and invertebrates. You should make sure you have a tight-fitting lid on your aquarium. Although Chili Rasboras are not known for jumping, they do sometimes try to leap out of the tank, and they’re so small, you run the risk of losing them.
Gorgeous creatures, Chili Rasbora have a dark stripe along the side of their red bodies. This dark stripe is contrasted with a deep red stripe above the dark one. They also have small dark spots at the base of the anal and tail fins. Male Chili Rasbora can be distinguished from females by looking at dorsal and anal fins, which have vivid red stripes. At 1.8cm, these beauties are truly nano fish.
To enjoy the best color possible, make sure you provide your Chili Rasboras with a planted aquarium with floating plants and a dark substrate. Fine texture sand or gravel is ideal for the nano Chili Rasboras.
These conditions will also encourage the best health for these tiny fish. In their natural environment in Borneo, they make their home in blackwater streams and pools, so the dark substrate will meet their inclination for the dark bottom. Their natural habitat also includes soft water with a low pH, so they will need that in your home aquarium, too.
They will appreciate a lush environment that has both planted and floating plants. Roots and branches mimic their environment and hanging vegetation limits the direct light to the Chili Rasboras. Although you can keep them as a smaller school of six in a 20L nano tank, if you keep them in a larger tank, you will have enough room for a huge and stunning school, which will produce a moving light show in your aquarium. If you include live plants in your tank set up, they will not only have a blanket to explore, but the floating plants will also make a home for plankton and worms, which are just the right sized snack for tiny Chili Rasbora mouths. The plant cover, as we mentioned, will dim the light in the tank, which encourages the development of more intense and vivid colors.
Chili Rasbora’s natural environment has a slow flow of water, so you should create the same water conditions in your home tank. These fish are extremely small and they will not be able to handle a strong current. To counteract any current that would be too strong, add branches, driftwood, logs, and other decorations to break up the current. Also, the plants will help with the current, too.
They do need a filter because they require pristine water in order to survive; just make sure the filter is not too strong. Because they are so small, any change in water condition could be fatal, so you need to monitor and maintain stable parameters. In addition to a slow current, Chili Rasboras prefer water that is both soft and acidic. You’ll need a test kit to monitor levels, and you could use distilled water or reverse osmosis to dilute tap water to create the proper conditions.
If you need to lower the pH level, there are natural remedies that can be used instead of additives These include almond leaves – these natural additions will release tannins that in turn reduce the pH. The presence of tannins and the low pH it provides is beneficial for the Chili Rasbora’s health, reducing pathogens in the water and making sure they don’t get sick.
The optimal parameters to ensure a close match to their natural habitat are:
- GH: 1-2
- KH: 3-12 dKH
- pH: 4.0-7.0
- Temperature: 20°-28° C
Although Chili Rasboras have this wide acceptable temperature parameter, they do require the stability we talked about, so be sure to maintain a constant temperature. For this reason, don’t be fooled by the low end of the temperature range and think that you don’t need a heater. Variations in room temperature can lead to variations in tank water temperature, and chilly water creates stress to fish. Stressful fish have compromised health, lifespan, coloration, and mood. Set the heater to a point on the acceptable range of 20°-28° C and maintain it for happy, healthy, and stress-free Chili Rasboras.
In addition to maintaining a temperature that is not too cold, you also want to make sure that the temperature is not too hot–Chili Rasboras can easily be overheated by long periods of direct sunlight (another reason that the plant cover is beneficial for these nano fish.)
Although they are omnivores, Chili Rasboras prefer a carnivorous diet. Offer them a variety of flakes, pellets, and freeze-dried, fresh, or frozen protein sources like bloodworms and chopped micro worms. To ensure the best color and health of your Chili Rasbora, make sure you give them varied sources of nutrition. Be mindful not to overfeed these fish–they are very small and can get sick if they eat too much, and also the more they eat, the more waste they create, which can dirty the water and make them sick. One final thing to remember is that due to their nano size, they need all food chopped and pulverized. Flakes, for example, should be crushed to powder form. Ideally, you feed them something like Tropical Nanovit Granulat, Tropical Mikro-Vit Hi-Protein or Tropical Prodefence Hi-Protein powder food.
It is very important to keep Chili Rasbora’s tank impeccably clean. You should clean the substrate and perform partial water changes regularly. They are strong fish, but they are very small and they are very sensitive to changes in water conditions, and cannot tolerate a dirty tank.
When they are ready to breed, the male Chili Rasboras turn a brighter red, so you can tell them apart from the female. In addition, the black and red markings on their dorsal and tail fins become darker. Females, on the other hand, will look rounder and plump because they are carrying eggs.
Watch out because the male Chili Rasboras can get a little territorial at breeding time, and they may fight, so you need to make sure that you have enough space for them to each have their own little area. You may see the male Nanos showing off to get the female’s attention. If he gets it, the female will lay a small number of eggs that she scatters on the tank’s bottom. And that is where the parenting ends. Neither the male nor the female Chili Rasbora actively care for their eggs at all. In fact, they have been known to cannibalize their own eggs.
If your home aquarium is dense enough, the fry may have enough cover to survive despite the threat of other fish in the tank having them for a midnight snack (never mind their own parents!) However, if you are hoping to breed the Chili Rasboras in earnest, you should set up a separate breeding tank. They spawn pretty constantly, so in a separate breeding tank, you have the chance to give the fry a fighting chance to live. You can feed the fry infusoria and paramecium until they can handle larger foods.
To create the best balance for breeding, you will need 1 to 2 females for every male in the tank, and you’ll need males that are dominant. The breeding tank setup should be as follows: Add small groups to spawning containers, with mesh at the bottom that is large enough that the eggs can fall through but small enough that the parents cannot access the eggs and eat them.
It’s kind of fun to see them spawning–they look like they are chasing each other around the tank. The male and female Chili Rasbora can be kept in the breeding tank for three or four days and then they should be moved back to the main tank. If you leave them in the breeding tank for longer than that, the Chili Rasbora fry are at risk.
Remember that Chili Rasbora is especially sensitive to water changes, so if you are using a breeding tank, you must make sure that the temperature, slow, pH, and hardness is consistent in both tanks; otherwise, you are likely to lose the fish in the transfer as they can not tolerate the instability.
The available specimen of this nano fish are around 1-1.5 cm in size.