rm
Passport
- Family
- Rasbora
- Grows to
- 4.5 cm (1.8")
- Lives
- 5–8 years
- Temperament
- Peaceful
- Care
- Beginner
- Swims
- Mid-water
- Keep
- In a group of 8 or more
- Water
- 21–28 °C (70–82 °F)
MalaysiaSingaporeIndonesia
Care requirements
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On record for Harlequin Rasbora: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level, tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 57 L / 15.0 US gal
- pH 5–7.5
- Hardness 1–12 dGH
- Diet micropredator
- Tank length 60 cm minimum
Care notes written from general aquarium knowledge, not from the cited sources.
About
The community fish that asks for the least and gives back the most. Harlequins are hardier than neons, calmer than danios, too small to bother anything and too quick for much to bother them. When a tank needs a mid-water shoal and nothing else about the stocking is settled, this is usually where you land.
That black wedge on the flank is how you know one, and it deepens as the fish settles in. If yours look washed out, they are either stressed or newly moved.
They shoal properly, too — a loose, coordinated group that holds together out in open water instead of scattering. You only get to see that with numbers.
Tank setup
Harlequins love a group, and they want to be seen in one. Keep too few and they'll hang at the back and lose their colour; give them a proper shoal and they'll take the middle of the tank and stay there.
Go dark underneath them and break up the light overhead. Like most blackwater fish their colour answers their surroundings, and the same fish over pale gravel under a bright lamp looks like half the animal.
Plant the sides and leave the middle open. They use that mid-water and they want it clear, with cover close enough to duck into.
Soft, slightly acidic water suits them best, though they're genuinely tolerant and will do fine outside it as long as it holds steady.
Feeding
Harlequins are small, unfussy eaters. Good flake, micro pellets, frozen daphnia and baby brine shrimp all go down well. They feed in mid-water and at the surface, and they're quick enough to get their share in most communities.
Watch the mouth size, though. Anything they can't swallow whole gets ignored and then rots in the substrate.
Avoid: big pellets, and one heavy feed a day — they do better on two small ones.
Filtration and flow
Keep the flow gentle to moderate. These come from slow, tannin-stained forest streams and have no interest in fighting a current.
Stable beats pristine with harlequins. They'll forgive a wide range of parameters and they're much less forgiving of a sudden change, which is the usual story with soft-water shoalers.
Botanicals and leaf litter suit them and really bring the colour out.
With plants
Completely safe, and one of the easiest fish you can put in a planted tank. No digging, no eating, nothing uprooted.
They'll use broad leaves as a spawning site, which is worth knowing if you keep cryptocorynes — more on that below.
Health
They're hardy, and the usual community problems hit them mildly. Most losses trace back to going into an immature tank rather than to anything specific to the species.
Colour is what you watch. A harlequin that stays pale and hangs at the back for days, rather than for a few hours after a change, is worth looking into.
They'll pick up ich after a temperature swing, like most small shoalers.
Breeding
This one's unusual and worth a go. Harlequins don't scatter their eggs — the female turns upside down under a broad leaf and lays them on the underside, and the male fertilises them there.
Cryptocoryne leaves are the classic spawning site, and plenty of people keep the two together for exactly that reason.
You'll need soft acidic water and a separate tank, because the adults eat the eggs. The fry are very small and want infusoria before they can handle anything else.
Tank mates
Avoid9
- Convict Cichlid Convict Cichlid grows to 15 cm against Harlequin Rasbora at 4 cm, big enough to eat it.
- Jewel Cichlid Jewel Cichlid grows to 15 cm against Harlequin Rasbora at 4 cm, big enough to eat it.
- Pictus Catfish Pictus Catfish grows to 12 cm against Harlequin Rasbora at 4 cm, big enough to eat it.
- Common Goldfish Common Goldfish is not safe with Harlequin Rasbora: common goldfish and rasbora are a bad pairing.
- Demasoni Cichlid Demasoni Cichlid is not safe with Harlequin Rasbora: african cichlids and rasbora are a bad pairing.
Only with care6
- Chinese Algae Eater Chinese Algae Eater is aggressive and Harlequin Rasbora is peaceful.
- Bala Shark Bala Shark is a risk to Harlequin Rasbora: rasbora and sharks are a pairing to watch.
- Paradise Fish Paradise Fish is a risk to Harlequin Rasbora: large gouramis and rasbora are a pairing to watch.
- Pearl Gourami Pearl Gourami is a risk to Harlequin Rasbora: large gouramis and rasbora are a pairing to watch.
- Silver Dollar Silver Dollar is a risk to Harlequin Rasbora: rasbora and silver dollar are a pairing to watch.
No conflict is recorded with the other 89 species in the database, so nothing to flag. 4 species are not covered at all, so they could not be judged either way.