Exclamation Point Rasbora (Boraras urophthalmoides)

The Exclamation Point Rasbora (Boraras urophthalmoides) is a small, very resistant and peaceful freshwater fish, but it doesn’t adapt very well to community fish tanks due to its size and shy nature.

The species is found in the basins of the Sai Buri, Mae klong and Chao Phraya rivers in the southern peninsula of Thailand, where they live in shallow water places such as swamps, ponds and rice paddies. The water in these environments is usually quite soft and acidic and sometimes stained with tannins.

Some groups of these fish have also been found in Cambodia and Vietnam, where they inhabited moats and lakes within the Angkor Wat temple complex near Siem Reap. A very common aspect of all these environments mentioned is that they have abundant vegetation, that is, the Exclamation Point Rasbora prefers densely planted fish tanks.

Technical Details

Name: Exclamation Point Rasbora, Least Rasbora, Sparrow Rasbora, Spice Rasbora;

Scientific Name: Boraras urophthalmoides (Kottelat, 1991);

Family: Cyprinidae;

Species Origin: South Asia (Cambodia, Thailand and Vietnam;

Length: Up to 1,5 inch;

Life Span: 4 – 5 years;

Care Level: Easy / Moderate;

Water Parameters

pH: Maintain the pH of the water between 6.0 – 7.0;

Water Hardness: Between 8° – 12°dH;

Temperature: Must be kept between 24 – 28°C (Celsius);

Care

Food

In an fish tank, Exclamation Point Rasbora will accept high quality feeds such as micropellets and crushed flakes, but they should not be fed just that.

You should provide live and frozen foods every day like brine shrimp, daphnia and bloodworms to improve the fish color and also encourage them to get into breeding conditions.

Temperament / Behavior

The Exclamation Point Rasbora is a schooling fish by nature and therefore should be kept in groups of at least 8 to 10 fish.

Keeping them in large groups will not only help make them feel safer, but will also result in a more colorful and natural looking colors, like that seen in the wild. The males will also display their best colors and some interesting behaviors as they compete with other males for the females’ attention.

The fish usually swims in the middle and upper region of the fish tank.

Tank Mates

As much as the Exclamation Point Rasbora is a very peaceful fish, it’s still not ideal for community fish tanks due to its small size and shy nature. It will do best when kept in groups of its own species or with other very small species.

If you want to mix them with other fish, try to put them with Microdevario, Sundadanio, Danionella, Eirmotus, Trigonostigma, pygmeu cory and small catfish, like Otocinclus catfish.

In addition, you can add them with more timid species of anabantids such as, for example, Sphaerichthys and Parosphromenus.

Good tank mates also include caridina and neocaridina shrimps.

Breeding / Mating

Like many other cyprinids, the Exclamation Point Rasbora spawns continuously and doesn’t exhibit any parental care. This means that in good conditions and with the presence of males and females, you can see small eggs being laid almost daily.

In a well-established fish tank, it’s possible for small fry to appear without any intervention. However, if you plan on raising as many fry as possible, you will need to set up a separate fish tank.

The breeding environment should be poorly lit and with a background full of fine-leaved plants such as java moss. When spawning, the eggs will fall through the leaves of these plants and the adults will not be able to reach them.

The water should be slightly acidic with the temperature getting a little higher than normal. Filtration is not necessary, but if you want, you can put in a small filter to oxygenate the water a little.

See Also:

• Otocinclus Catfish (Otocinclus Affinis);

Then add two or three pairs of well-conditioned adult fish to the breeding tank. Transfer them slowly to avoid high stress levels, but if conditions are good, they should start spawning the next morning.

As much as these fish feed on their eggs, they still don’t seem to look for them like many other cyprinids. Once spawning has started, it should continue daily. Keep pairs for no more than a few days before removing them, as the first eggs should start to hatch on the second day after the original spawn.

The fry are quite small and will survive from their yolk sacs for about 24 hours. After that, you will have to feed them with infusoria or other special food for fry.

About a week later, the fry should be big enough to accept brine shrimp and microworm.

Wait a week or two to perform small partial water changes to avoid unnecessary shocks to the fry.

Fish Tank Size

The fish tank needs to have at least 10 gallons for a group of ten fish of this species.

Although it’s a small fish, the Exclamation Point Rasbora needs space to swim and dominant males will form temporary territories when they spawn.

Try to keep them in densely planted tanks, but don’t forget to add floating plants, roots, and logs to lessen the amount of incoming light, as they seem to appreciate slightly darker environments.

Filtration doesn’t have to be strong, as in the wild these fish inhabit fairly sluggish waterways and can suffer if there is a rough current.

Finally, avoid placing them in an fish tank that is not fully cycled and with stabilized parameters, as they are very sensitive fish.

References

Rainboth, W.J., 1996. Fishes of the Cambodian Mekong. FAO species identification field guide for fishery purposes. FAO, Rome, 265 p. (Ref. 12693)