Exclamation Point Rasbora Care Guide: Tiny and Eye-Catching

The exclamation point rasbora (Boraras urophthalmoides) is a charming nano fish named for the distinctive marking on its body that resembles a punctuation mark. Tiny, colourful and perfectly suited to planted nano tanks, this Southeast Asian micro fish is an excellent choice for Singapore hobbyists exploring the world of small-scale aquascaping. This exclamation point rasbora care guide covers everything you need to keep these diminutive fish thriving.

About the Exclamation Point Rasbora

Boraras urophthalmoides was originally described in 1914 and has had a somewhat complicated taxonomic history, having been placed in several genera before finding its current home in Boraras. It is native to Southeast Asia, with populations found in Thailand, Cambodia and Vietnam, where it inhabits shallow, slow-moving waters, rice paddies and peat swamp margins.

The common name “exclamation point rasbora” refers to the distinctive body marking: a dark elongated dash on the flanks with a separate round spot near the tail base, forming a pattern that resembles the punctuation mark “!”. It is also sometimes called the least rasbora or sparrow rasbora, though exclamation point rasbora is the most widely used common name.

Like all Boraras species, this is a genuinely tiny fish, reaching a maximum of approximately 2 cm. It is one of the smallest fish commonly kept in aquariums and is exclusively suited to nano and small tank setups.

Appearance and Identification

The exclamation point rasbora has a subtle but attractive appearance:

• Base body colour is golden-amber to warm orange, becoming more vivid with good care
• A prominent dark lateral dash runs along the mid-body, tapering towards the front
• A separate dark round spot sits at the base of the caudal fin, forming the “dot” of the exclamation mark
• Fins are mostly transparent with faint orange or yellow tinting
• The belly is typically lighter, sometimes silvery
• Maximum size approximately 2 cm

The colour of exclamation point rasboras intensifies considerably in the right conditions. Fish kept in bare, bright tanks look washed out and pale. In blackwater-style setups with tannin-stained water, dark substrate and dense planting, the warm amber-orange body colour becomes remarkably rich.

Males tend to be slightly slimmer and more intensely coloured than females. Gravid females appear noticeably plumper when viewed from above. The differences are subtle and easier to spot in mature, well-conditioned fish.

Tank Requirements

Exclamation point rasboras are schooling fish that must be kept in groups. A minimum of ten is essential, and larger groups of fifteen to twenty display far more confident, natural behaviour. In groups of fewer than eight, these fish are perpetually nervous, hiding among plants and rarely venturing into the open.

Tank setup should prioritise dense planting and gentle conditions. A sponge filter provides adequate filtration without creating currents that overwhelm these tiny fish. If using a powered filter, always baffle the output and cover intakes with fine sponge to prevent the fish from being trapped.

Exclamation point rasboras are mid-water swimmers that occupy the central region of the tank. They tend to hover in loose schools among plant stems and driftwood, occasionally darting after micro food particles. Provide a mix of open swimming areas and planted refuges.

Indian almond leaves, driftwood and alder cones are excellent additions. They release tannins that soften and acidify the water, replicating the blackwater conditions these fish experience in the wild. The amber water tint also enhances their warm body colours.

Water Parameters

Singapore’s soft tap water is a good match for exclamation point rasboras. The pH may be slightly higher than ideal, but these fish are somewhat more adaptable than some of their Boraras cousins. Adding botanicals and driftwood helps bring the pH down naturally.

The ambient temperature of 28-30 C in Singapore is at the upper end of their range. Exclamation point rasboras tolerate this reasonably well, particularly in well-oxygenated, planted tanks. Nano tanks positioned in air-conditioned rooms will benefit from slightly cooler, more stable temperatures.

Water quality is paramount in nano tanks. Perform weekly water changes of 20-25% using dechlorinated water. PUB uses chloramine in Singapore’s water supply, so always use a conditioner that specifically neutralises chloramine. In small-volume nano tanks, even trace amounts of chloramine can harm these delicate fish.

Feeding Micro Foods

The most important feeding consideration for exclamation point rasboras is food size. Their mouths are minuscule, and standard aquarium foods are far too large:

• Best foods: live or frozen baby brine shrimp, cyclops, daphnia (small species)
• Dry foods: finely crushed micro pellets, powdered flake food, micro granules designed for nano fish
• Live cultures: vinegar eels, micro worms, infusoria
• Natural grazing: biofilm and microorganisms on plant surfaces and hardscape

Feed small amounts two to three times daily. Baby brine shrimp (live or frozen) is the gold standard food for all Boraras species. It is the perfect size, highly nutritious and eagerly accepted. If you can maintain a brine shrimp hatchery, your exclamation point rasboras will reward you with their best colour and condition.

In a mature, well-planted tank with driftwood and botanicals, a significant amount of the fish’s diet comes from natural grazing on microorganisms. This is one reason why heavily planted, mature setups produce the healthiest, most vibrant fish. A newly set-up tank lacks this biofilm layer, so supplementary feeding is even more important in the early months.

Tank Mates

At just 2 cm, exclamation point rasboras can only be kept with other very small, non-threatening species:

• Other Boraras species (phoenix rasboras, chili rasboras)
• Cherry shrimp and crystal shrimp
• Pygmy corydoras (Corydoras pygmaeus, C. hastatus)
• Ember tetras
• Small snails (nerite, ramshorn)
• Otocinclus catfish (in larger nano setups)

Any fish large enough to fit an exclamation point rasbora in its mouth is a threat. This rules out the majority of common community fish, including most tetras, barbs, gouramis and livebearers. Even a honey gourami, generally considered one of the most peaceful community fish, can intimidate or prey on fish this small.

A species-only tank or a carefully curated nano community of similarly sized species is the safest and most rewarding approach. Cherry shrimp are particularly good companions, as they occupy different niches and add visual interest without posing any threat.

Comparison With Other Boraras Species

The Boraras genus contains several species commonly available to Singapore hobbyists. Here is how the exclamation point rasbora compares. For a comprehensive look at the entire genus, see our Boraras species guide.

All Boraras species share similar care requirements and can be kept together. Mixing species in a nano tank creates a visually interesting display with varied colour and pattern, while all fish benefit from the increased school size and activity.

Breeding

Exclamation point rasboras are continuous spawners in suitable conditions. They scatter eggs among fine-leaved plants and moss, typically depositing a few eggs each day rather than spawning in a single large event:

• Eggs are adhesive and attach to plant surfaces, particularly moss
• Adults will eat eggs and fry if they find them
• Fry are extremely tiny, requiring infusoria or paramecium as first food
• In heavily planted tanks, some fry survive naturally
• Dense Java moss provides the best cover for eggs and newly hatched fry

For deliberate breeding, a small, heavily planted tank with gentle filtration and mature water gives the best results. Soft, acidic water (pH below 6.0) and a diet rich in live foods encourage spawning. The key to raising fry is the availability of sufficiently small first food, as the fry are among the tiniest of any aquarium fish.

Frequently Asked Questions

Are exclamation point rasboras hardy enough for beginners?

They are reasonably hardy for nano fish, but they are not the best choice for someone completely new to the hobby. Their small size means water quality issues in nano tanks can affect them quickly. A cycled, mature tank is essential. Beginners who have already successfully maintained a small planted tank for a few months should be comfortable keeping this species.

How do I tell exclamation point rasboras apart from other Boraras?

The “!” marking is distinctive. Look for the elongated dark dash along the mid-body combined with a separate round dark spot at the base of the tail. Chili rasboras have a continuous lateral stripe, phoenix rasboras have a single prominent blotch and dwarf rasboras (B. maculatus) have multiple spots. The exclamation point pattern is unique among the genus.

Can exclamation point rasboras live in community tanks?

Only if the community consists entirely of similarly tiny, peaceful species. Standard community fish (tetras, barbs, gouramis, livebearers) are too large and will either eat or intimidate exclamation point rasboras. They do best in species-only nano setups or carefully curated nano communities with other micro fish and dwarf shrimp.

Do exclamation point rasboras need a heater in Singapore?

No. Singapore’s ambient temperature of 28-30 C is at the upper limit of their tolerance but is manageable without a heater. A chiller is not strictly necessary either, though keeping the tank in an air-conditioned room can provide slightly cooler, more stable conditions that benefit the fish. Adequate oxygenation through gentle surface movement or a small airstone helps compensate for reduced oxygen at higher temperatures.

Explore the World of Nano Fish

Exclamation point rasboras prove that size is no barrier to beauty. A well-designed nano tank with a school of these tiny, marked fish is a captivating display. If you are looking to set up a nano aquarium or need advice on micro fish species, contact our team at Gensou or visit us at 5 Everton Park. We can help you design the perfect small-scale setup with our custom aquarium service, from desktop displays to built-in nano tanks for HDB and condo living.

Related Reading

• How to Breed Exclamation Point Rasboras: Tiny Eggs, Big Patience
• Exclamation Point Rasbora Care Guide: Boraras Urophthalmoides
• Exclamation Point Rasbora Care Guide: Brigittae Nano Gem
• How to Aquascape for Exclamation Point Rasboras: Dense Nano Jungle
• How to Breed Chili Rasboras: Micro Spawners in Soft Water