Epalzeorhynchos bicolor

The Red-tailed Black Shark is not a true shark, but a striking member of the minnow family. Its name comes from its shark-like body shape, deep black color, and a stunningly vibrant red tail. This contrast makes it a very popular fish in the aquarium hobby. It's an active creature, constantly exploring the middle and bottom levels of the tank, which is always entertaining to watch.

However, its beauty comes with a bold personality. This fish is known for being territorial, especially towards its own kind and other fish that look similar. Because of this, it's best to keep only one Red-tailed Shark in your aquarium to prevent constant fighting. It is an omnivore and not a picky eater, readily accepting a wide variety of commercial fish foods, from flakes and pellets to frozen treats and vegetables.

An interesting fact is that this species is critically endangered in its natural habitat in Asia. The fish you see in stores are all bred in captivity on large-scale fish farms. This ensures its survival in the hobby without impacting wild populations. Due to its size and active nature, a spacious tank is necessary to keep it happy and healthy.

The Red-tailed Black Shark, Epalzeorhynchos bicolor, is a classic cyprinid whose common name is a clever piece of marketing; it bears no relation to marine sharks. Its fusiform body shape and dynamic swimming style are what lend it the 'shark' moniker. This fish's primary appeal is its dramatic coloration: a velvety, jet-black body sharply contrasted by a brilliant, fiery red caudal fin.

Successful keeping of this species hinges on understanding its behavior. It is intensely territorial. While juveniles might tolerate each other, adults will establish a large territory and relentlessly harass any fish they perceive as a rival. This includes other Red-tailed Sharks, similarly shaped species like Rainbow Sharks, and even some bottom-dwellers that encroach on their space. Therefore, the golden rule is one per tank, unless the aquarium is exceptionally large (500+ liters) with extensive rockwork and planting to break lines of sight. When choosing tank mates, opt for robust, fast-swimming species that occupy the upper water column, such as larger danios, barbs, or tetras. Avoid slow-moving fish or those with long, flowing fins, as they are likely to be bullied.

A suitable habitat is crucial. The required large tank provides the necessary swimming room for this active fish. Decor should include plenty of hiding places like caves, driftwood tangles, and dense plantings. These structures not only offer security but also help to delineate territory, which can reduce aggression towards other tank inhabitants. A moderate water flow is appreciated, mimicking the riverine environments of its origin. A secure lid is a must, as these fish are fast and can easily jump out of an open-top aquarium.

As an omnivore, its dietary needs are straightforward but require variety for optimal health and coloration. A high-quality sinking pellet or wafer should form the staple of its diet. This must be supplemented with vegetable matter, such as blanched zucchini, spinach, or algae wafers. They are known biofilm and algae grazers, especially when young, but should not be relied upon as a primary 'clean-up crew'. Occasional protein-rich treats like frozen or live brine shrimp and bloodworms will be eagerly consumed.

Breeding in a home aquarium is considered nearly impossible. Commercial breeding is achieved on a massive scale in Southeast Asian farms, where hormonal injections are used to induce spawning. This commercial production is vital, given the species' critically endangered status in the wild, possibly even being extinct. All individuals in the trade are captive-bred, which is a point of conservation worth noting.

The Red-tailed Black Shark, Epalzeorhynchos bicolor, is a freshwater cyprinid belonging to the order Cypriniformes. Its genus name, Epalzeorhynchos, is derived from Greek, referring to its 'horn-like snout,' while the species epithet, bicolor, denotes its distinct two-toned coloration. Morphologically, it presents a laterally compressed, fusiform body optimized for locomotion in moderate currents. The mouth is subterminal and equipped with two pairs of small barbels, an adaptation for benthic grazing on aufwuchs, biofilm, and detritus.

This species exhibits a pronounced intraspecific and interspecific agonistic behavior. This territoriality is a significant consideration for its ex-situ management in aquaria. The behavior intensifies with sexual maturity and is directed towards conspecifics and other morphologically convergent species. In a closed system, this necessitates a large habitat volume and complex structures (hardscape and flora) to create visual barriers and refugia, thereby mitigating stress and physical harm. Failure to provide adequate spatial resources often results in chronic stress, susceptibility to disease, or mortality of subordinate individuals.

Physiologically, E. bicolor is relatively hardy, tolerating a broad range of pH and water hardness values, as indicated by the provided data. However, its medium metabolism and oxygen consumption rate, coupled with a moderate bioload factor, demand robust and consistent filtration. Efficient biological filtration is paramount to process nitrogenous wastes (ammonia, nitrite) into less toxic nitrate, while consistent water changes are needed to prevent the accumulation of dissolved organic compounds and nitrate. Water movement should be sufficient to ensure high levels of dissolved oxygen.

Reproduction in aquaria is exceptionally rare without hormonal induction. In commercial aquaculture, spawning is artificially induced using gonadotropic hormones like LHRH-a (Luteinizing Hormone-Releasing Hormone analogue). This practice is essential for the species' continued presence in the ornamental fish trade, as E. bicolor is listed as Critically Endangered (CR) on the IUCN Red List. Its native populations in Thailand have been decimated by habitat loss and fragmentation, primarily due to dam construction and agricultural pollution, to the point where it may be Extinct in the Wild (EW). Therefore, the entire global aquarium population is sustained by captive breeding programs.