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No federal permit to keepOpsarius pulchellus
Opsarius pulchellus
Fishes › Carp, barbs, minnows, loaches (Cypriniformes) › Danionidae (Danios and rasboras)
Opsarius pulchellus, is a species of fish in the family Danionidae, with the largest individual recorded being 11 cm long. "Pulchellus" is a Latin diminutive meaning "beautiful".
Intro from Wikipedia (CC BY-SA 4.0)
Care at a glance
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 4.3 in / 11 cm).
- Water: Freshwater.
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Diet: FishBase classes it as a carnivore.
- Availability: Rarely or never seen in the aquarium trade; expect to source it from specialists or not at all.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 47 × 18 in (roughly 64 US gallons); space needed is rated “large tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 64–79 °F, pH 6–7.5, 2–12 dGH.
- Behaviour: a shoaling fish best kept in a group of six or more; not a community fish.
- Difficulty: Moderate (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “The aquarium should ideally be designed to resemble a flowing stream or river with a substrate of variably-sized rocks, sand, fine gravel, and some larger water-worn boulders.”
- Tankmates: “Unsuitable for the general community due to its environmental requirements, and likely to outcompete or intimidate slow-moving and less bold species at meal times since it is an extremely fast swimmer and vigorous feeder.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Danios and rasboras
Applies to most species in this group. Habitat: These Asian fishes occupy habitats ranging from zebra-danio pools and rice paddies to shaded harlequin streams, rocky Devario streams and planted galaxy-rasbora wetlands. [fg159-zebra, fg159-harlequin, fg159-giant, fg159-galaxy]. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- Use at least 90 × 30 cm (36 × 12 in) for zebra danios.
- Harlequins require at least 60 × 30 cm (24 × 12 in), shaded planted cover and subdued light.
- Devario aequipinnatus needs at least 120 × 45 cm (48 × 18 in), oxygenated water, moderate flow and a tight lid.
- Galaxy rasboras need dense planting and broken sight lines in at least 45 × 30 cm (18 × 12 in), with gentle sponge filtration.
- Match chemistry: harlequins pH 5.0–7.5, 1–12 dGH; galaxy rasboras pH 6.5–7.5, 5–15 dGH.
Climate & lighting
| Water | 64.4–77°F |
Diet
- Quality flakes or granules sized to the fish.
- Live or frozen Daphnia and Artemia.
- Bloodworms for zebra danios, harlequins and Devario.
- Small sinking foods for galaxy rasboras, which rarely feed at the surface.
Social life
- Keep zebra danios and harlequins in groups of at least 8–10. Galaxy males spar: dense cover and larger groups distribute aggression. Active Devario can overwhelm timid feeders.
Health watch
- Pseudoloma microsporidiosis in zebra danios.
- Pleistophora infection and columnaris can produce similar white lesions in zebra danios.
- Nipped fins among rival galaxy males.
Understanding the animal
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater, in rivers and streams. Uses both the bottom and open water. Adults occur over gravel substrate in clear, swift, small streams up to rapidly flowing stretches of large rivers. Feed on insect larvae, especially odonatans. Rarely seen in the markets. |
| Water it lives in | Freshwater. |
| Climate | Tropical climate. |
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 88°F (up to 95°F in the hottest sampled areas) |
| Cool-season lows | about 52°F (down to 49°F in the coldest sampled areas) |
| Average temperature | 69–78°F across sampled records |
| Relative humidity | 71–74% on average (driest month about 59%) |
| Rainfall | about 1568 mm a year, with strong wet and dry seasons |
Measured at 60 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | Opsarius pulchellus, is a species of fish in the family Danionidae, with the largest individual recorded being 11 cm long. "Pulchellus" is a Latin diminutive meaning "beautiful". — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Wild diet | O. pulchellus feeds mainly on the surface of the water, feeding on dead insects that land on the surface. — Wikipedia (community-edited) |
| Biology | Adults occur over gravel substrate in clear, swift, small streams up to rapidly flowing stretches of large rivers. Feed on insect larvae, especially odonatans. Rarely seen in the markets. — FishBase |
| Conservation | O. pulchellus are rarely found in markets, but are exploited by subsistence fisheries and occasionally for the aquarium trade. Habitat degradation through sedimentation increase (e.g. by large-scale damming) may become problematic in the future, especially along the Mekong and Chao Phraya. — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Adult length
Maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates; aim for the middle.
pH
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 47 × 18 in (about 64 US gallons).
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Seriously Fish: Zebra danio (Danio / Brachydanio rerio) Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish: Trigonostigma heteromorpha Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish: Devario aequipinnatus Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish: Danio / Celestichthys margaritatus Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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