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Exclamation Point Rasbora© Melanochromis / Public domain

Exclamation Point Rasbora

The Exclamation Point Rasbora (Boraras urophthalmoides) is a tiny cyprinid from Southeast Asia, named for the dark stripe running along its body and the round black spot at the base of its tail fin — together they resemble an exclamation mark, which is exactly how the English name came about. In the wild these fish live in peat swamps and marshes with soft, weakly acidic water, and recreating those conditions calls for a bit of experience, which is why the species is generally considered suited to intermediate keepers. They are naturally peaceful shoalers, and a group swimming together brings out the best in their small, delicate bodies. Their calm temperament also makes them easy to combine with other similarly sized, gentle tankmates.

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Exclamation Point Rasbora key facts

Care level
Intermediate
Lifespan
2-4 years
Size
1.6cm SL (FishBase records up to 4cm TL)
Temperature
20〜28℃
Diet
Fine dried foods and live or frozen Artemia nauplii and daphnia
Tank
Seriously Fish suggests a 45 x 30cm base. A densely planted tank with driftwood, leaf litter and floating plants to diffuse the light suits it, and filter flow should be gentle, as it comes from sluggish water.
Water Temperature & Quality
Seriously Fish gives 20-28C, pH 6.0-7.0 and 1-10 dGH. It depends less on strongly acidic water than its congeners and does well in soft, slightly acidic conditions. In a small tank, change water often.
Tank Mates
Peaceful but small and timid, so not a general community fish. Other Boraras, plus Microdevario, Sundadanio, Danionella, Trigonostigma, pygmy Corydoras and Otocinclus, are good choices.
Diet & Feeding
Its mouth is very small, so use the finest dried foods. Live or frozen Artemia nauplii and daphnia improve colour and breeding condition. Feed small amounts several times a day.
Breeding & Spawning
An egg-scattering continuous spawner with no parental care. Given fish in good condition, a few eggs are laid every day, and in a mature, densely planted tank some fry survive unaided.
Health & Notes
Groups of eight to ten or more settle it and bring out colour. Published sizes differ widely between sources, so judge tankmates from the fish in front of you. The IUCN rates it Near Threatened and it is not covered by CITES.
TraitsSmall speciesShoalingSoft waterPlanted tank

About Exclamation Point Rasbora

A tiny Southeast Asian cyprinid whose black stripe and tail-spot resemble an exclamation mark. Prefers soft, weakly acidic water and is generally rated for intermediate keepers; shoals beautifully.

7 things to know before welcoming a Exclamation Point Rasbora

  1. 1Prefers Soft, Acidic Water

    In the wild these fish live in the peat swamps and marshes of Southeast Asia, so they thrive in soft, weakly acidic water. Filtering through soil substrate or peat helps keep water chemistry stable.

  2. 2A Natural Shoaling Fish

    Kept in a group rather than alone, this rasbora shows more of its natural behavior and its tiny body looks far more lively. Shoaling together is also thought to reduce stress.

  3. 3The "Exclamation Mark" Pattern

    The dark stripe along the body paired with the round black spot at the base of the tail resembles an exclamation mark — the source of both its English and Japanese names. It's also a useful clue for telling it apart from closely related Boraras species.

  4. 4Choose Small, Peaceful Tankmates

    Because this fish is extremely small, avoid housing it with large or aggressive species and stick to similarly sized, peaceful tankmates. It also tends to do well alongside invertebrates such as shrimp.

  5. 5Feed Fine, Small Food

    Its mouth is very small, so powdered or finely crushed food is easiest for it to eat without leftovers. Offering small amounts several times a day helps ensure even nutrition.

  6. 6Sensitive to Sudden Water Changes

    Being so small, this fish is sensitive to sudden shifts in water quality or pH. Take time acclimating new arrivals, and change water in small, frequent amounts rather than large infrequent ones.

  7. 7Why It's Rated for Intermediate Keepers

    Maintaining stable, soft, weakly acidic water and staying alert to changes in water quality are what place this species in the intermediate category. It helps to understand the basics of water management before bringing one home.

Frequently asked questions about Exclamation Point Rasbora

Q.Is this fish suitable for beginners?
A.This species is generally rated for intermediate keepers, so some prior experience with water quality management is recommended. Beginners who can maintain stable, soft, weakly acidic water can still succeed with it.
Q.Can it be kept with other fish?
A.Because it's so small, it does best with similarly sized, peaceful tankmates. Avoid pairing it with large or aggressive fish.
Q.What tank size does it need?
A.With a standard length of around 1.6 cm, this is an extremely small fish best kept in a group, so choose a tank with enough room for several to shoal comfortably. Maintaining soft, weakly acidic water is equally important.
Q.Where does its name come from?
A.The dark stripe along its body combined with the black spot at the base of the tail looks like an exclamation mark, which is how it got the English name "Exclamation Point Rasbora." This distinctive marking is the same feature behind its Japanese name.
Q.Are there any regulations to be aware of?
A.This species is not subject to CITES.

Useful tools for Exclamation Point Rasbora care

💧Aquarium Volume CalculatorCalculate water volume, weight, and heater wattage from tank dimensions🧪Water Quality CheckerFind compatible fish, shrimp, plants & corals based on pH, temperature & hardness🍽️Feeding GuideCheck feeding frequency, portion sizes & supplements by species and growth stage🤝Compatibility CheckerCheck compatibility between two species on a 5-level scale📊Fish Compatibility MatrixCheck fish compatibility at a glance with our matrix chart🔄Nitrogen Cycle GuideAuto-calculate bacteria colonization timeline for new tank cycling🗓️Seasonal Care CalendarMonthly care events and seasonal management tips at a glance🚿Water Change CalculatorAuto-calculate optimal water change frequency and volume by tank size and fish count🐠Stocking CalculatorCalculate max fish capacity for your tank size with overstocking alertsElectricity Cost SimulatorCalculate monthly and annual electricity costs for care equipment with presets🧬Breeding PlannerSelect parent varieties to view breeding schedules and offspring patterns🏞️Tank Layout PlannerGet substrate, plant & hardscape suggestions based on tank size and style🧮Care Cost SimulatorEstimate initial, monthly & annual costs by category, care level and quantity⚖️Species Comparison ToolCompare two species side by side: care difficulty, size, lifespan & temperature🎯Pet Match DiagnosticAnswer 7 questions to find your top 3 perfect pets📋Lifetime Cost SimulatorEstimate lifespan and lifetime costs by species for dogs, cats, reptiles and more🚚Transport Safety CheckerCheck transport safety score and precautions by category, season, method and distance💊Medication Dosage CalculatorCalculate proper medication dosage by body weight and medicine type for fish, reptiles, and small animals⏱️Quarantine & Acclimation TimerManage quarantine periods and acclimation steps with countdown timers. Includes recommended durations by species

Learn more about Exclamation Point Rasbora in the encyclopedia

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Care difficulty, lifespan, size and diet — all basics covered.

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