About Harlequin Rasbora
The Harlequin Rasbora is a classic and highly popular aquarium fish known for its distinctive copper-orange body and striking black wedge-shaped patch on the rear half of its body. Native to Southeast Asia, specifically Thailand, Malaysia, and Singapore, these fish inhabit slow-moving streams, peat swamps, and forest pools often stained dark with tannins. Their name comes from the harlequin pattern of their markings. They are incredibly hardy and adaptable, making them excellent choices for beginners while still satisfying experienced aquarists with their peaceful demeanor and active schooling behavior. Harlequins are mid-water swimmers that prefer to be in groups, creating beautiful displays as they swim together in synchronized movements. Their long lifespan and easy care requirements have made them a staple in community aquariums worldwide for decades.
Care Guide
Care Requirements
Tank Setup
Harlequin Rasboras appreciate a well-planted tank with open swimming areas in the middle. Use aquatic mosses, cryptocoryne, and java fern to provide cover while maintaining clear sightlines. Dark substrate and subdued lighting from floating plants enhance their colors and reduce stress. A gentle filter flow mimics their natural habitat.
Water Quality
- Temperature: 72-81°F (22-27°C)
- pH: 6.0-7.5
- Water Hardness: Soft to moderate (2-15 dGH)
- Ammonia/Nitrite: 0 ppm
- Nitrate: <30 ppm
These fish are adaptable but prefer stable conditions. Regular water changes (25% weekly) keep them healthy and vibrant.
Feeding
Omnivorous and easy to feed. Offer a varied diet:
- High-quality flake or micro pellet food as staple
- Frozen foods: daphnia, bloodworms, brine shrimp 2-3 times weekly
- Live foods for conditioning or as treats
- Occasional vegetable matter
Feed small amounts 2-3 times daily. They have small stomachs and prefer several small meals.
Behavior & Compatibility
Peaceful and sociable, Harlequins must be kept in schools of 6 or more, ideally 10+. They establish a hierarchy within the group and display fascinating schooling behaviors when kept in adequate numbers. They swim primarily in the middle water column and make excellent community tank inhabitants. Compatible with nearly all peaceful species of similar size.
Common Health Issues
- Ich (White Spot Disease): Common stress-related illness; treat with temperature increase and medication
- Fin rot: Usually due to poor water quality; improve conditions and treat with antibiotics if severe
- Swim bladder issues: Often caused by overfeeding; fast fish and feed peas
Breeding
Moderately difficult to breed. They are egg scatterers that prefer breeding on the underside of broad leaves. Conditioning with live foods and slightly acidic, soft water encourages spawning. Remove adults after spawning to prevent egg predation. Fry are tiny and require infusoria initially.
Tips for Success
- Buy larger schools for best behavior and color display
- Allow 2-3 weeks for new fish to settle and show full colors
- Add Indian almond leaves or driftwood for natural tannins
- Keep with peaceful tank mates only
- Monitor water parameters weekly despite their hardiness