Epalzeorhynchos bicolor (Red Tail Shark)

10 July 2026

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The Red Tail Shark, native to Thailand, is a striking and highly popular freshwater fish. Known for its deep velvety black body and vibrant red tail, this semi-aggressive cyprinid adds dynamic movement and a touch of drama to sufficiently large, well-structured community aquariums.

Epalzeorhynchos bicolor (Red Tail Shark)

Overview

The Red Tail Shark, scientifically known as Epalzeorhynchos bicolor, is an iconic freshwater fish cherished by aquarists for its stunning contrast of colors and active, shark-like swimming behavior. Despite its common name, it is not a true shark but a member of the Cyprinidae family. It is a solitary and territorial species that requires careful consideration when choosing tank mates.

Image of firetail epalzeorhynchos labeo bicolor

Distribution and Habitat

Endemic to Thailand, the Red Tail Shark originally inhabited the clear waters and floodplains of the Chao Phraya River basin. Unfortunately, due to habitat destruction and overfishing, it is currently listed as Critically Endangered in the wild. Virtually all specimens available in the aquarium trade today are captive-bred in commercial facilities.

Description of Red Tail Shark

Body shape:

They possess an elongated, streamlined body with a flattened ventral surface, giving them a distinctly shark-like silhouette.

Color:

The body is a deep, velvety black that provides a stark and beautiful contrast to their brightly colored tail.

Barbels:

They have two pairs of small barbels located near the mouth, which assist in locating food along the substrate.

Snout:

The snout is pointed and slightly downturned, perfectly adapted for scraping algae and scavenging on the bottom.

Eyes:

Their eyes are relatively large, dark, and positioned on the sides of their head to provide a wide field of vision.

Fins:

The dorsal fin is prominent and erect, often featuring a subtle white tip on the leading edge. The pectoral, pelvic, and anal fins are completely black.

The Tail:

The most defining feature is the deeply forked, vibrant red or bright orange-red caudal fin, which stands out brilliantly against the dark body.

Temper

Red Tail Sharks are known for their semi-aggressive and highly territorial temperament. As they mature, they become increasingly intolerant of other bottom-dwelling species and are extremely aggressive toward their own kind or fish with similar body shapes and colors.

Sociality

Due to their territorial nature, it is highly recommended to keep only one Red Tail Shark per aquarium. They do best in a community tank with robust, fast-moving mid-to-top dwelling fish like larger tetras, barbs, or danios that will not compete for bottom territory.

Activity

They are highly active and energetic fish. You will often see them constantly patrolling their established territory, grazing on algae, and actively chasing away any fish that encroaches on their space.

Keeping and Caring for Red Tail Shark

Tank size:

A minimum tank size of 55 gallons is required to provide enough swimming space and territory. Larger tanks are preferred to minimize territorial disputes with tank mates.

Water Parameters:

Temperature

They thrive in tropical temperatures ranging from 22 to 26°C (72-79°F).

pH

The ideal pH level is slightly acidic to neutral, between 6.5 and 7.5.

Hardness

Water hardness should be kept moderate, ideally between 5 and 15 dGH.

Ammonia, Nitrite, Nitrate

Ammonia and Nitrite must be maintained at 0 ppm, while Nitrates should be kept below 20 ppm through regular water changes.

Lighting

Moderate lighting is sufficient, which also helps encourage a healthy amount of algae growth for them to graze on.

Water flow

They appreciate moderate to strong water flow, which simulates the riverine environments of their natural habitat.

Decorations and Plants

Provide plenty of hiding spots using caves, driftwood, and rocks. Dense planting is also recommended to break lines of sight and help define territorial boundaries.

Diet

Red Tail Sharks are omnivorous scavengers. In the aquarium, they will readily accept high-quality sinking pellets, flakes, and algae wafers. Their diet should be supplemented with live or frozen foods such as bloodworms, brine shrimp, and daphnia, as well as fresh vegetables like blanched zucchini, cucumber, or spinach.

Some Feeding Tips

Feed them once or twice a day, ensuring that enough food reaches the bottom of the tank. Providing a varied diet is crucial for maintaining their vibrant coloration and overall health.

Breeding

Breeding the Red Tail Shark in a home aquarium is considered extremely difficult, primarily due to their intense aggression towards conspecifics. In commercial settings, breeding is achieved in large vats using hormone injections to induce spawning.

Conclusion

The Red Tail Shark is a captivating and dynamic centerpiece for the larger community aquarium. While their territorial nature requires careful planning regarding tank mates and layout, their striking appearance and active behavior make them a highly rewarding species for aquarists who can meet their needs.

Fish info

Care level: Moderate
Temperament: Semi-aggressive
Adult size: 12-15 cm
Life expectancy: 5-8 years
Fish type: Cyprinid
Temperature : 22-26°C
pH: 6.5-7.5
Color Form: Black, Red

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