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Least Rasbora
Boraras micros
Animalia›Chordata›Actinopterygii›Cypriniformes›Cyprinidae
📍 Thailand
Arguably the smallest rasbora — under half an inch fully grown. A translucent body with red and black markings. For dedicated nano setups only.
Care Guide
Diet
Least Rasboras are omnivores requiring high-quality micro pellets and small flake foods as staples. Supplement 2-3 times weekly with tiny frozen foods like brine shrimp nauplii, daphnia, or micro bloodworms to promote color and condition. Feed small amounts once daily, only what they can consume in 2-3 minutes.
Behavior
Least Rasboras are peaceful, schooling fish that must be kept in groups of at least 10 to display natural behavior and reduce stress. They are active mid-water swimmers with a gentle temperament, spending most of their time foraging and interacting with their school. They are easily startled by sudden movements and prefer calm, well-planted environments.
Breeding
Breeding Least Rasboras in captivity is difficult and rarely achieved by hobbyists. They require very soft, acidic water (pH 5.0-6.0), dense vegetation for egg scattering, and pristine water conditions. Fry are extremely small and require infusoria or liquid fry food for the first week before accepting micro foods.
Tank Mates
Similar water requirements and peaceful temperament; shrimp won't prey on adult rasboras
Larger shrimp that coexist peacefully in planted nano tanks with similar pH/temperature needs
Comparable size and peaceful nature; both prefer soft, slightly acidic water
Similar nano-sized fish with peaceful temperament and overlapping water parameters
Peaceful bottom-dweller that won't compete for mid-water space; helps maintain tank cleanliness
Hardy plant that provides shelter and won't be uprooted by these tiny, gentle fish
Common Diseases
Ich (White Spot Disease)
White spots on body and fins, rapid breathing, lethargy, rubbing against objects
Raise temperature gradually to 28-29°C, perform daily 25% water changes, use aquarium salt at half-dose for nano tanks, or treat with ich-specific medication if severe
Fin Rot
Frayed or deteriorating fin edges, discoloration at fin bases, lethargy
Improve water quality with frequent partial water changes, remove any sharp decorations, treat with antibacterial medication if infection spreads
Bacterial Infection
Cloudy eyes, sores on body, loss of appetite, erratic swimming
Perform daily 50% water changes, maintain pristine water conditions, treat with broad-spectrum antibiotic medication if condition worsens
Stress-Related Illness
Faded coloration, hiding, loss of appetite, increased susceptibility to disease
Ensure minimum school size of 10, provide dense vegetation for security, maintain stable water parameters, reduce tank disturbances
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Quick Facts
- pH
- 5.0–7.0
- diet
- omnivore
- maxSize
- 0.5 inches
- minTankSize
- 5 gallons
- temperature
- 72–82°F (22–28°C)
Temperature
72–82°F
22–28°C