Harlequin Rasbora (Trigonostigma heteromorpha)

Very much so — it's an all-time community classic. Hardy, undemanding on water (pH 5.0–7.0), content at 22–25 °C, and accepts any food. The only real rules: keep a school (8+, their security is collective) and avoid aggressive tankmates. First tank? This species succeeds at very high rates.

Six minimum, eight to fifteen ideally. Harlequins are superior schoolers among small cyprinids — enough numbers produce tight, organized cruising; too few and they sulk in corners. Ten in 50 L is the classic; larger tanks make the display grander.

Omnivore and unfussy: fine pellets, flakes, frozen bloodworms, brine shrimp. Its terminal, slightly upturned mouth takes floating and mid-water food naturally; bottom micro-pellets require a deliberate dip. Rotate the diet (dry + frozen + occasional live) to keep the metallic rose-violet sheen at its best.

Nearly any peaceful community fish: neons, cardinals, guppies, corydoras, small plecos, gentle dwarf cichlids, adult shrimp. Avoid: tiger barbs and cross-band types (fin-nippers), large fish (stress by presence), and hyper-aggressive feeders. Harlequins are mid-tier competitors — confirm they're getting their share.

Three usual causes: too small a school causing chronic stress (fix: add companions), water too hard and alkaline for its preference (GH over 12, pH over 7 mutes it — soften), or diet lacking color enhancers (add spirulina and astaxanthin-rich foods). The copper-violet shimmer is a health barometer — whether it flashes under light tells you the fish's state.

Challenging but doable. The key is simulating native soft acidic water: pH 5.5–6.0, GH 1–2, 26–28 °C, with dense planting — especially broad-leaf plants, since harlequins deposit eggs on the undersides of leaves, hanging upside-down to spawn. Parents eat eggs, so remove adults after spawning; eggs hatch in 24–36 hours and fry need infusoria or superfine powder first foods.

The harlequin (Trigonostigma heteromorpha) is larger (3.5–5 cm) with its signature black triangular patch and rose-copper body; neons carry the neon red-blue stripe; cherry barbs are wine-red all over. All three mix perfectly and star in the classic community tank together. Only the harlequin spawns upside-down on leaves — each species has its own appeal.

For community fish, check water first (ammonia or nitrite spikes — most common), then aggression (bite marks on the corpse), then age. Normal lifespan is 4–6 years; if everyone else is fine and parameters test clean, a single death may simply be an individual event — do a quarter water change and observe. Don't overreact.

Not mandatory, but strongly recommended. Its natural habitat is slow streams and swamps of Southeast Asia; dense planting is its security blanket — planted tanks show looser schooling and richer color. Anubias, Java fern, and moss need no strong light; floating plants for surface shade also match the native setting.

Four to six years is normal, seven with fine care. It's the fish that accompanies a beginner into expertise — buy a school and they'll still be there when you're a veteran. Compared with annual mini-tetras, the harlequin's time investment pays back handsomely, which is why it has topped community sales charts for decades.