1 kinds · tap one for a closer look
Peaceful copper-colored schooling fish with a black triangle patch.
370 species in our list are a good match.
Peaceful schooler for planted tanks.
Flakes, micro-pellets, frozen foods.
Tap a food to see what it is.
Males are slimmer and more colourful with a sharper-edged black triangle; females are rounder-bellied, often a little larger, with a more rounded triangle.
Common problems. Tap one to see the signs. This is a guide, not a diagnosis.
Egg-depositor (plants) · Hard
Pairs attach small batches of eggs to the underside of broad leaves; eggs hatch in 24-48 hours and fry swim freely after about a week.
Buy a group of 8-10 and let them pair up. Condition on live foods.
30-40 L tank with soft acidic water (pH 5.5-6.5), broad leaves like Cryptocoryne and dim light.
Soft acid water, warm temperature and conditioning with live foods.
Around 50-100 eggs on leaves; hatch in about 24-36 hours.
Feed infusoria, then baby brine shrimp. Fry are sensitive; keep water soft and clean.
Recognised by its black triangle. It lays eggs on the underside of broad leaves, unusual for a small cyprinid.
German ichthyologist Georg Duncker described the harlequin rasbora in 1904. It reached Europe in the early 20th century and became a staple of planted tanks. Its black triangular patch is its trademark.
First described by Georg Duncker in 1904.
14 facts checked with sources
Originally described as Rasbora heteromorpha. Seriously Fish notes Tang et al. (2010) proposed folding Trigonostigma back into Rasbora, but Catalog of Fishes currently treats Trigonostigma as valid.
Eschmeyer's Catalog of Fishes: heteromorpha, Rasbora · Seriously Fish: Trigonostigma heteromorphaOlder sources (e.g. NParks Singapore) still list Cyprinidae; current classification is Danionidae, subfamily Rasborinae.
Eschmeyer's Catalog of Fishes · FishBase: Trigonostigma heteromorphaSeriously Fish: 45 mm SL (aquarium), and 'maximum 32 mm SL in nature, though captive specimens may grow slightly larger'. FishBase: 5.0 cm TL.
Seriously Fish: Trigonostigma heteromorpha · FishBase: Trigonostigma heteromorphaSite range lies inside Seriously Fish's 21-28 °C; FishBase gives a narrower 22-25 °C.
Seriously Fish: Trigonostigma heteromorpha · FishBase: Trigonostigma heteromorphaSite range is inside Seriously Fish's 5.0-7.5; FishBase tops out at 7.0. Site could widen the lower end to 5.0.
Seriously Fish: Trigonostigma heteromorpha · FishBase: Trigonostigma heteromorphaSite range is inside Seriously Fish's 1-12 dGH.
Seriously Fish: Trigonostigma heteromorpha · FishBase: Trigonostigma heteromorphaSeriously Fish: 60 x 30 cm base 'should be the smallest considered since this species should be maintained in numbers'. 60 x 30 x 30 cm (height = depth) = 54,000 cm³ = 54 L; Seriously Fish itself gives ~54 L.
Seriously Fish: Trigonostigma heteromorphaGovernment source describing wild fish: upper and middle levels. 'Middle' is supported; 'upper-middle' would be more exact. FishBase calls it benthopelagic.
NParks Singapore Flora & Fauna Web: Trigonostigma heteromorphaSeriously Fish difficulty rating reads 'Easy'.
Seriously Fish: Trigonostigma heteromorphaCatalog of Fishes covers the Malay Peninsula (which includes southern Thailand and Singapore) and northern Sumatra plus nearby islands. Seriously Fish treats Sumatra/Borneo records as less certain.
Eschmeyer's Catalog of Fishes · Seriously Fish: Trigonostigma heteromorphaSite has no breeding text; compared with legacy. Egg-placement claim confirmed. Hatch time 24-48 h (legacy said 24-36 h). The legacy '50-100 eggs' count is unsourced; Seriously Fish only says eggs come in 'small batches'.
Seriously Fish: Trigonostigma heteromorpha · FishBase: Trigonostigma heteromorpha