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Care guide · Freshwater · fish

Dwarf rasbora

Boraras maculatus

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The dwarf rasbora, Boraras maculatus, is a miniature fish in the family Danionidae. Eschmeyer’s Catalog of Fishes accepts the name in Danionidae: Rasborinae; older sources use the combination Rasbora maculata. It is peaceful, but its tiny size and shy nature make it a poor automatic choice for a busy community aquarium. A calm shoal, stable water and food that fits its small mouth matter more than high stocking or bright lighting. Before buying, check that existing tankmates are small and calm enough.

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At a glance

Temperature
20–28 °C
pH
4.0–6.5
GH
1–5 °dGH
Aquarium length
At least 45 cm
Minimum aquarium volume
At least 41 L
Adult size
At least 2.5 cm
Group size
At least 8–10 individuals
Temperament
Peaceful

About this species

Seriously Fish and FishBase report a maximum standard length of 25 mm. Standard length ends at the tail base and excludes the caudal fin. The species name maculatus refers to a spotted pattern. Boraras naevus looks similar, but in B. maculatus the red coloration extends onto the head; in B. naevus it does not. Colour varies among populations, so compare several traits and never substitute a photograph of a related species.

Natural habitat

The specialist species profile records the range as Peninsular Malaysia, southern Thailand, eastern Sumatra, Singapore and Bintan. Natural habitat includes slow blackwater streams and rivers associated with old peat-swamp forest. Fallen leaves and other organic matter release tannins; conditions are often very soft and acidic. These habitats face pressure from forest clearing, agriculture and development. The precise collection origin of aquarium fish is not always known.

Aquarium and layout

Despite its miniature size, the shoal needs swimming room. Seriously Fish recommends a minimum base of 45 × 30 cm, about 41 litres at its reference height. This accounts for swimming and temporary male territories during spawning. Provide dense planting, floating plants, roots and sheltered areas while leaving open water. Keep current gentle and introduce the fish only after the aquarium is biologically mature and stable.

Water conditions

The specialist profile gives 20–28°C, pH 4.0–6.5 and GH 1–5 dGH. These are care ranges within a natural setting of very soft, acidic water, not instructions to force the pH rapidly to a target. Abrupt changes can be stressful. Test the source water, choose a stable approach suited to the fish and acclimate them slowly. Keep ammonia and nitrite at zero and maintain careful routine husbandry.

Behaviour and group size

Boraras maculatus is very peaceful but shy. The specialist source recommends at least 8–10 conspecifics; a larger shoal can show more natural behaviour if the aquarium supports it. Large, fast or dominant fish may intimidate the dwarf rasboras or regard them as prey. A species-only tank is therefore a sound default. Any companions should be similarly tiny and calm and tolerate the same soft water. Check that every fish gets enough food.

Feeding

Stomach analyses cited by FishBase indicate a micropredator feeding on small insects, worms and crustaceans. For aquaria, Seriously Fish recommends tiny live or frozen foods such as water fleas and brine shrimp, alongside dried foods of suitable size; it advises against feeding dried food exclusively. Crumble flakes or use fine particles, feed small portions and check that the shyest fish actually eat. Remove leftovers to protect water quality.

Breeding

Seriously Fish describes continuous spawning: small numbers of eggs may be laid daily, with no parental care. Fry may occasionally appear in a mature, planted aquarium, but adults can eat eggs and larvae. For deliberate breeding, the specialist source describes a separate soft, acidic tank with fine-leaved plants and egg protection. The very small larvae need microscopic first foods. Treat breeding timelines as source-specific guidance rather than a guarantee for every aquarium.

Sources & review

This care guide draws on several specialist sources and was last checked on .

View the sources