Blackline Rasbora
Rasbora borapetensis
Danionidae
About
A slim, silvery rasbora from the slow shallows of the Mekong, Chao Phraya and Mae Klong basins and the northern Malay Peninsula, where it fills ditches, ponds, canals and reservoir margins and tolerates water far murkier than most hobby fish will accept. A crisp black line runs along the lower flank from the gill cover to just short of the tail, a gold stripe glows immediately above it, and the base of the caudal fin carries a warm red-orange flush; the fins themselves stay clear of black pigment. Unlike the Trigonostigma harlequins it is usually shelved beside, it wears a straight line rather than a wedge. It is a restless, tightly co-ordinated shoaler that patrols the middle and upper water and ranks among the most peaceful cyprinids in the trade.
Care
Keep 8-10 or more together in at least 70 litres on a 60 cm footprint, with gentle flow, soft to neutral water and plenty of planting. A dark substrate and floating cover bring out the gold and red. Hardy and forgiving of beginner mistakes, but keep the tank lidded because it jumps.
Diet
Feed small flake, micro-granules and crushed pellets as the base, and add frozen or live daphnia, artemia and bloodworm most days. Live food visibly excites them and produces the strongest colour.
Tankmate compatibility
Gets along with (71)
Possible with care (100)
Avoid (100)
Computed by the AquaSage engine for a spacious reference tank — always check the full verdict for your exact setup in the calculator.
Telling males from females
What works for this species, most reliable first.
- Belly depthA hint only · only on well-fed adults, and only as a comparison
For most tetras, barbs and rasboras this is all there is: a conditioned female is deeper through the belly than a male of the same length.
Also in these lists
Frequently asked questions
- What tank size does a Blackline Rasbora need?
- A Blackline Rasbora needs an aquarium of at least 70 litres (18.5 US gallons) with a footprint at least 60 cm (23.6 in) long — for this species, swimming length matters as much as raw volume.
- What water parameters does a Blackline Rasbora need?
- Blackline Rasbora does best at 22–26 °C (71.6–78.8 °F), pH 6–7.5 and a general hardness of 2–12 °dGH.
- What group size does a Blackline Rasbora need?
- Blackline Rasbora is a social species — keep a group of at least 8 so natural behaviour emerges and stress stays low.
- Is the Blackline Rasbora suitable for beginners?
- Yes — Blackline Rasbora is one of the easier species to keep and forgives typical first-tank mistakes, as long as the aquarium is cycled and maintained.