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Harlequin rasboras are peaceful, easy-going shoaling fish with a copper glow and a distinctive black triangle. A tight shoal moving through a planted tank is one of the best sights in fishkeeping, and they're hardy enough for beginners.
Harlequin rasboras at a glance
| Size | 4–5cm |
| Minimum tank | 60 litres |
| Group size | At least 8, ideally 10+ |
| Temperature | 23–27°C |
| pH | 6.0–7.5 (soft water preferred) |
| Lifespan | 5–8 years |
Choosing your fish
Pick from the standard harlequin rasbora or the long-fin harlequin. Browse more species in our rasbora range.
Setting up the tank
- Plants: harlequins come from slow, heavily planted waters. Dense planting at the back and sides with open swimming space at the front suits them perfectly. See live plants.
- Dark substrate and soft light: their colours glow over a darker substrate. Floating plants help soften the light.
- Gentle flow: avoid strong currents.
- Soft water: they adapt to moderately hard water, but colour and breeding are best in soft, slightly acidic water. Catappa leaves and driftwood help. Read pH, GH and KH explained.
Feeding
Harlequins are micropredators. Offer small foods such as crushed flake, micro pellets and frozen daphnia, cyclops and brine shrimp. Feed small amounts once or twice a day.
Tankmates
Keep them with other small, peaceful fish:
- Neon and cardinal tetras
- Corydoras and otocinclus
- Dwarf and honey gouramis
- Peaceful bettas in a well-planted tank
Avoid large or boisterous fish that could eat or bully them.
Breeding
Unusually, harlequins lay their eggs on the underside of broad leaves such as anubias or cryptocorynes. Spawning is most likely in soft, warm water at around 26–28°C.
Common problems
Harlequins are hardy in clean water. Most problems come from new tank syndrome or poor water. Test regularly with a test kit, and quarantine new fish. See how to set up a quarantine tank.
