The Exclamation Point Rasbora (Boraras urophthalmoides), also known as the least rasbora or sparrow rasbora, is a type of Rasbora fish native to southeast Asia and produces electric red-orange hues in a dark-water aquascape. These peaceful shoaling fish are an excellent addition to a well-researched tank, as they are easy to care for and display interesting behaviors during breeding cycles.
| Common Name(s) | Exclamation Point Rasbora, Least Rasbora, Sparrow Rasbora |
| Scientific Name | Boraras urophthalmoides |
| Origin | Southeast Asia |
| Temperature | 68-80.6°F (20-27°C) |
| Size | 1 in (2.5 cm) |
| Minimum Tank Size | 15 gallons (54 L) |
| Food & Diet | Omnivore |
| Lifespan | 4-8 years |
| Water pH | 6.0-7.0 |
| Tank Mates | Sundadanio, Microdevario, Eirmotus, Danionella, Trigonostigma, pygmy Corydoras |
| Breeding | Egg scatterer |
| Disease | Ich, velvet, fungal infections |
Table of Contents
Exclamation Point Rasbora Care
Exclamation point rasboras are best suited for densely planted aquaria with floating plants and driftwood branches or roots to aid light diffusion. With origins in the sluggish waters of southern Thailand, least rasboras may struggle with swift currents, so water filtration should not be too strong.
Like many rasboras, the exclamation point rasbora is peaceful yet timid by nature. While most easily maintained in a single-species tank, least rasboras can make quality companions for shy anabantoids and other miniature species. As shoaling fish, exclamation point rasboras gain confidence and provide a robust, eccentric display when sustained in schools of 8-12 individuals. Males will also produce their best colors and interesting behaviors when competing for female attention.
pH & GH
Exclamation point rasboras require a water pH of 6.0-7.0 and a GH (general hardness) of 8-12. Maintaining healthy water conditions is imperative to keep your fish healthy; remember to check your water’s acidity and hardness regularly.
Food & Diet
Exclamation point rasboras are omnivorous by nature, preying on small insects, crustaceans, worms, and zooplankton in the wild. In aquaria, fish flakes or pellets will work; however, daily meals of micro-crustaceans and small worms will result in the best coloration of the fish and provide ideal breeding conditions.
Feeding tiny fish like exclamation point rasboras may prove challenging, so try crushing your fish flakes or pellets before feeding your little friends.
Are Exclamation Point Rasboras Hardy?
Exclamation point rasboras are not the hardiest fish as they are very timid by nature, and males can become territorial during breeding. Sparrow rasboras do best when kept in their own aquarium or alongside other minuscule species like Sundadanio, Microdevario, Eirmotus, Danionella, Trigonostigma, or pygmy Corydoras.
Exclamation Point Rasbora Size
The minuscule exclamation point rasbora may only grow up to about 1 inch long. Like other rasbora species, female least rasboras are noticeably rounder-bellied than their more vibrant-colored male counterparts.
Exclamation Point Rasbora Tank Size
A school of 8-12 exclamation point rasbora will require a 15-gallon tank, but as always, the bigger, the better. Male sparrow rasboras may become territorial when breeding, so be sure to maintain adequate space and vegetation for your school.
How many Exclamation Point Rasboras should be kept in a 5-gallon tank?
Keeping a school of exclamation point rasboras in a 5-gallon tank is not recommended. If this tank size is necessary, it’s wise to maintain it as a species-only aquarium, with only 2-4 least rasboras at most.
Tank Setup
A tank temperature of 68-80.6°F (20-27°C), water pH of 6.0-7.0, and GH of 8-12 will make for a comfortable and healthy environment for your exclamation point rasboras. Originating in the sluggish waters of southern Thailand, sparrow rasboras require warm, soft, and acidic water with low to moderate current flow to survive and thrive.
Exclamation point rasboras are an excellent choice for densely planted aquaria equipped with floating plants and driftwood pieces to dissipate light as their electric colors glimmer through the clear, dark water aquascape.
Do Exclamation Point Rasboras need a heater?
Since exclamation point rasboras require tank temperatures between 68-80.6°F (20-27°C), having a reliable aquarium heater is necessary. While it may not always be in use, having a functioning heater is the only way to be prepared for those colder months or aquarists in temperate or colder climates.
Daily temperature checks with a calibrated thermometer are helpful to ensure your sparrow rasboras are comfortable daily.
Schooling Behavior & School Size
Exclamation point rasboras naturally live in large schools, so it’s recommended to maintain schools of at least 8-12 in an aquarium. Larger schools of least rasboras will develop confidence among them and create a naturally stunning visual display as males produce more vibrant colors and display interesting behaviors when competing for female attention.
Exclamation Point Rasbora Tank Mates
The exclamation point rasbora is not usually recommended for community aquaria due to the timid nature of the miniature fish. They are most easily kept in either a single-species tank or an aquarium with similar-sized species that enjoy similar conditions, such as Sundadanio, Microdevario, Eirmotus, Danionella, Trigonostigma, or pygmy Corydoras.
Due to their shy personalities, least rasboras should be kept in schools of 8-12 to promote confidence in your fish.
Exclamation Point Rasbora and Betta
Exclamation point rasboras may be able to coexist with a betta fish in a well-researched aquarium. The best tank mates for betta fish are peaceful bottom dwellers; however, dwarf schooling fish that are quick enough to minimize chasings are also ideal. Including hiding places will create a more comfortable environment for these species to coexist.
Since sparrow rasboras may become territorial when breeding, and betta fish view new tank mates as intruders, the betta fish must always be added to the aquarium last, regardless of tank size. Fin-nipping and other aggressive behavior might occur if the introductions and tank environment are not set up and maintained properly. Sometimes your betta fish may be too aggressive to allow any aquarium companions, so be sure to supervise your introductions.
Exclamation Point Rasbora and Cherry Shrimp
Cherry shrimp and exclamation point rasboras will get along peacefully in a biologically mature aquarium. Both are peaceful species that require low filtration and similar water conditions. Natural spawnings of rasbora fry may not occur since cherry shrimp will eat the eggs.
Setting up a tank inclusive for sparrow rasboras and cherry shrimp should be simple as they require aquaria with densely packed plants and rocky substrate. Since cherry shrimp will need to groom themselves, moss is a necessity. Cherry shrimp can be introduced at a rate of 2 to 5 shrimp per gallon; however, they breed quickly, so having an aquarium that is too big is favored over having a tank too small.
Exclamation Point Rasbora and Neon Tetra
Exclamation point rasboras and neon tetras should be compatible in a well-researched, biologically mature aquarium. While rasboras originate in southeast Asia and tetra come from near the Amazon River Basin, they require similar water conditions and observe similar schooling behaviors.
Sparrow rasboras and neon tetras can make for a jaw-dropping visual effect in a dimly lit, densely planted aquarium if they are kept in schools to decrease timidity. Remember to ensure your rasboras and tetras have enough space to swim without becoming territorial.
Exclamation Point Rasbora vs. Chili Rasbora
Exclamation point rasboras and chili rasboras (mosquito rasboras) are incredibly similar in nature and appearance. Both fish are highly susceptible to changes in water chemistry and require biologically mature aquaria. With sparrow rasboras and mosquito rasboras in the same tank, maintaining schooling numbers is necessary to build confidence and decrease territorial behavior in your fish.
It may be challenging to differentiate between exclamation point rasboras and chili rasboras as they look nearly identical. In contrast with the chili rasbora’s vibrant scarlet scales, the exclamation point rasbora will appear slightly translucent, most noticeably on its fins. Both species are schooling fish that require similar water conditions and nutrition, so they are easily kept in a tank large enough to house both schools. A dimly lit, densely planted aquarium with schools of exclamation point rasboras and chili rasboras will produce a stunning aquascape for any aquarist.
Exclamation Point Rasbora Breeding
In a biologically mature, well-furnished aquarium with large schools of exclamation point rasbora conditioned to the tank, eggs will be scattered daily over the dense vegetation and decor. Sparrow rasboras display zero parental care, however, small numbers of fry may begin to appear without intervention, and some may survive into adulthood.
If you desire an increased yield of fry, a more controlled method is required:
While the adults can still be conditioned together, one or more separate breeding containers should be set up. Arrange these containers with very dim light and either leave the base of the tank bare or with a mesh-type material with a grade large enough to allow any eggs not caught by the plant to pass through where the adults cannot feed on them. Plastic ‘grass’-type matting can also be used and is readily available at most fish stores.
The water should have a pH of 5.0-6.5 with a temperature between 75-80.6°F. A clump of java moss or another fine-leaved plant should be added to fill roughly half of the available space. An expensive aquarium filter isn’t necessary, but a small air-powered sponge filter may be used.
2-3 pairs of well-conditioned adult rasboras should be added to each container. (It’s recommended to transfer them slowly to avoid increasing stress levels, but if conditions are proper, they should begin to spawn within 24 hours.
Like many small cyprinids, exclamation point rasboras will certainly eat their eggs, but they won’t actively hunt for them. Once spawning begins, it should continue daily.
The pair(s) should be left in place for no longer than a couple of days before being taken out of the container since the first eggs will hatch within 24-48 hours after the initial spawning. The tiny fry will live on their yolk sacs for about a day until they require Paramecium or other micro-foods.
After 7 to 10 days, the fry should be large enough to accept microworms and brine shrimp. With the passing days, the additional fry should begin to appear from later spawnings. It’s advised to wait 1 to 2 weeks before slowly conditioning the young with small water changes to avoid shocking them.
Exclamation Point Rasbora Lifespan
With a healthy diet and a suitable environment within the aquarium, exclamation point rasboras can live for about 4 to 8 years. Always practice good tank maintenance habits like regular water condition checks, water changes, and tank cleaning.
