fish · Danionidae
Blackline rasbora
Rasbora borapetensis
Wild range: Mekong, Chao Phraya, and Mae Klong basins (Thailand, Cambodia, Laos, Vietnam) and northern Malay Peninsula; also recorded from China; introduced/non-native records from Philippines and parts of the Sunda Islands; type locality Bung Borapet (Bueng Boraphet), Nakhon Sawan, central Thailand (Asia)
At a glance: Blackline rasbora care
Compiled reference information. Review the care notes and original sources below.
What temperature is listed for Blackline rasbora?
The compiled profile lists 22.0–26.0 °C for Blackline rasbora (Rasbora borapetensis). Check the original sources below for context and differing recommendations.
What tank size is listed for Blackline rasbora?
The profile lists a minimum tank volume of 18.0 US gallons (68.0 liters). Volume alone does not establish suitability; consider dimensions, group size and other inhabitants alongside the full care notes.
What pH is listed for Blackline rasbora?
The compiled profile lists a pH of 6.0–7.5. Review the cited care sources alongside the other water parameters in this profile.
Natural habitat
Shallow margins of gently flowing or still waters — ponds, ditches, canals, swamps, flooded fields, and reservoir edges usually ≤2 m deep; often somewhat turbid; midwater to surface; hardy and adaptable, including disturbed/polluted localities (Seriously Fish, FishBase).
Where they are found
Catalog primary locked as Rasbora borapetensis Smith, 1934 per trade, ITIS TSN 163746 (valid; English red-tailed rasbora), FishBase SpecCode 10834, Eschmeyer’s Catalog of Fishes (Current status Valid as Rasbora borapetensis Smith 1934; type locality Bung Borapet, Nakorn-Sawan, central Thailand; CoF spid 30748; family Danionidae: Rasborinae), and IUCN. Not transferred to Trigonostigma (that genus holds former Rasbora such as T. heteromorpha/espei/hengeli). Remains in Rasbora (Liao et al. 2010 R. semilineata species group with R. rubrodorsalis and R. semilineata). Distinct from sympatric lookalike R. rubrodorsalis (bright red blotch in dorsal fin; R. borapetensis dorsal colourless, red confined to caudal-fin base). Older trade Cyprinidae family label superseded in CoF/FishBase by Danionidae — catalog uses Danionidae to match sibling rasbora rows.
Aquarium care
Beginner-friendly Southeast Asian schooling rasbora for planted community tanks (Seriously Fish, AquaticCommunity, Tropical Fish Keeping, Atlarium). Lock ≥18 US gal / ~68 L with a long footprint for a group of 8–10+ (SF 60×38×30 cm / ~68 L for a small group; Atlarium ≥60 L / ~15 gal; Tropical Fish Keeping 20 gal; OATA ≥60 L for 5 cm+ rasboras). Dark substrate, dense side/back planting, floating plants and wood to diffuse light, open midwater swim lane; gentle filtration only — may struggle in strong current (SF, AquaticCommunity). Water: locked 22–26°C, pH 6.0–7.5, GH 2–12 (SF 22–26 / 6.0–7.5 / 2–12; FishBase wild 22–26 / pH 6.5–7.0 / dH ≤12; AquaticCommunity 22–26 / 6.0–7.0; Atlarium 22–26 / 6–7.5 / GH card 2–15 with text 5–12; Tropical Fish Keeping 22–26 / 6.5–7.0 / 5–12 — locked overlapping practical band). Secure lid (can jump when startled).
Feeding
Micropredator/omnivore: wild diet insects, worms, crustaceans, and zooplankton (Seriously Fish, FishBase). Accepts quality flake and micro-pellets; colour and condition improve with daily small live/frozen Daphnia, Artemia, and bloodworm (SF, AquaticCommunity, Tropical Fish Keeping, Atlarium). Feed 2–3 small meals daily; clear uneaten food promptly.
Compatibility
Very peaceful community fish; keep in schools of ≥8–10 so they colour up and stay less nervous (SF, Tropical Fish Keeping, Atlarium). Compatible with other small cyprinids/rasboras, tetras, livebearers, rainbowfish, anabantoids, Corydoras, and loaches of similar temperament; avoid large or aggressive tankmates. Distinct from R. rubrodorsalis (red dorsal blotch) and from black-lined lookalikes such as R. einthovenii (black pigment in fins). Communitysafe; not nanook for a proper school.
Breeding
Egg-scatterer without parental care; continuous spawning when well conditioned (SF, Tropical Fish Keeping, AquaticCommunity). Use a dim, slightly acidic to neutral, warm (~upper temp band) spawning tank with mesh or fine plants so eggs fall out of reach; remove adults after spawning. Typical batches 30–50 eggs; hatch 18–48 h; free-swimming 24–48 h later. Start fry on Paramecium/infusoria, then Artemia nauplii/microworm. Home breeding is moderate difficulty — possible but less automatic than many tetras.
Sources
Compiled from multiple independent care sheets — not copied from a single site.