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Harlequin Shark
Labeo cyclorhynchus
📍 Central Africa (Congo River Basin)
The Harlequin Shark (Labeo cyclorhynchus) is a striking freshwater fish from Africa, featuring a dark body adorned with a distinctive pattern of spots and a bright orange-red tail fin. It is a popular choice among intermediate to advanced aquarists for its bold appearance and active nature. Despite its name, it is not a true shark but belongs to the Cyprinidae family and can become territorial as it matures.
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Care Guide
Diet
The Harlequin Shark is an omnivore that primarily grazes on algae and biofilm, making it a useful tank cleaner. Feed sinking algae wafers, spirulina pellets, and blanched zucchini or spinach as staples, supplemented with occasional bloodworms or brine shrimp. Feed once or twice daily, offering only what can be consumed within a few minutes.
Behavior
This species is active and spends most of its time in the lower to middle regions of the tank, grazing on surfaces and exploring. It can be territorial and aggressive toward other bottom-dwelling fish or similarly shaped species, especially in smaller tanks. It is generally best kept singly or with robust, fast-moving tankmates that occupy different swimming zones.
Breeding
Breeding the Harlequin Shark in captivity is extremely rare and has not been reliably documented in home aquaria. In the wild, they are believed to spawn seasonally in response to environmental triggers such as water temperature changes and rainfall. Hobbyists should not expect successful breeding without specialized facilities.
Tank Mates
Fast-moving and robust enough to avoid harassment; occupies mid-water zones
Active schooling fish that stays out of the shark's territory
Hardy and active, tends to stay in mid-water away from bottom territory
Peaceful schooling fish occupying mid to upper zones, unlikely to conflict
May compete for algae and bottom territory; monitor for aggression
Occupies upper zones and is generally peaceful, reducing territorial conflict
Common Diseases
Ich (White Spot Disease)
Small white spots resembling salt grains on body and fins, flashing, lethargy
Raise temperature to 28-30 C gradually, treat with ich medication such as malachite green or copper-based treatments; ensure good water quality
Fin Rot
Frayed, discolored, or deteriorating fins; may show redness at the base
Improve water quality with frequent water changes; treat with antibacterial medication such as kanamycin or erythromycin
Velvet (Oodinium)
Gold or rust-colored dust-like coating on skin, rapid gill movement, flashing against surfaces
Dim tank lighting, treat with copper-based medication or formalin; maintain optimal water parameters
Bacterial Infection
Ulcers, open sores, redness, swollen abdomen, loss of appetite
Isolate affected fish, perform water changes, and treat with broad-spectrum antibiotics such as kanamycin or nitrofurazone
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Quick Facts
- diet
- Omnivore – algae, sinking pellets, blanched vegetables, and occasional protein-rich foods
- lifespan
- 5-8 years
- max size
- 15 cm (6 in)
- tank size
- 55 gallons minimum
- temperament
- semi-aggressive
Water it likes
- ph
- 6.5-7.5
- ammonia
- 0 ppm
- nitrate
- <20 ppm
- hardness
- 5-15 dGH
- temperature
- 73–81°F (23–27°C)