Common Name: Harlequin Shark
Scientific Name: Labeo cyclorhynchus
Other Names: Harlequin Algae Eater, Variegated Shark
The Harlequin Shark is a striking and territorial freshwater fish known for its elongated body, bold patterning, and aggressive nature. Its coloration typically consists of a mix of dark brown to black patches interspersed with golden-yellow or orange markings, giving it a unique and eye-catching appearance. Like other Labeo species, it has a downturned mouth adapted for grazing on algae and biofilm. While it is a fascinating addition to larger aquariums, its territorial nature means careful tank mate selection is required.
Habitat and Distribution:
Native to Central Africa, Labeo cyclorhynchus is found in the Congo River basin, where it inhabits fast-moving rivers and streams with rocky substrates and dense vegetation. These waters are well-oxygenated and provide plenty of hiding spots among submerged roots, driftwood, and rocks.
Size and Lifespan:
The Harlequin Shark grows up to 6-8 inches (15-20 cm) in captivity, though wild specimens may reach slightly larger sizes. With proper care, they can live for 8-12 years.
Diet and Behavior:
This species is an omnivorous grazer, feeding on algae, plant matter, and small invertebrates in the wild. In captivity, they require a diet of high-quality sinking algae wafers, spirulina flakes, and occasional protein sources such as bloodworms, brine shrimp, or insect larvae. While juveniles may seem peaceful, they become increasingly territorial as they mature, often defending their preferred hiding spots aggressively.
Breeding and Reproduction:
Breeding Labeo cyclorhynchus in captivity is extremely rare and largely undocumented. In the wild, they are believed to migrate for spawning during the rainy season. Their territorial nature makes it difficult to keep multiple individuals in home aquariums without aggression issues.
Aquarium Care and Tank Requirements:
A minimum of 75 gallons is required for a single adult, with a larger tank (100+ gallons) preferred for a well-structured habitat. Their ideal tank setup includes a soft sand or fine gravel substrate, plenty of driftwood, caves, and rocky structures for territory establishment, strong filtration and moderate water flow to replicate riverine conditions, and subdued lighting with shaded areas to reduce stress.
Ideal Tank Mates:
The Harlequin Shark is highly territorial, especially toward other bottom-dwelling fish. Suitable tank mates include robust, fast-moving fish such as Congo Tetras, African Butterfly Fish, Synodontis Catfish, and large Barbs. Avoid other Labeo species, slow-moving bottom dwellers, or similarly shaped fish that may trigger aggression.
Difficulty Level:
Intermediate to Advanced. They require a large tank, careful tank mate selection, and a structured environment to prevent territorial disputes.
Water Parameters:
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Temperature: 74-82°F (23-28°C)
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pH: 6.5-7.5
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General Hardness (GH): 5-15 dGH
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Carbonate Hardness (KH): 4-10 dKH
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Ammonia: 0 ppm
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Nitrite: 0 ppm
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Nitrate: <20 ppm (regular water changes required)
Additional Information:
- As they mature, their aggression increases, requiring a well-structured tank with plenty of hiding spots.
- They require high-quality water conditions and a strong current to mimic their natural habitat.
- Unlike true algae eaters, they need a more varied diet to maintain optimal health.
The Harlequin Shark is a fascinating but challenging species best suited for experienced aquarists with the space to accommodate its territorial nature. With proper care and tank planning, it can be a striking and rewarding addition to a large freshwater aquarium.
