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17/02/2008

Bala shark

The Bala shark, Balantiocheilos melanopterus, also known as the tricolor shark, silver shark, or shark minnow, is a fish species of the family Cyprinidae, and has long been considered the sole member of the genus Balantiocheilos. This species is not a true shark, but is commonly called a "shark" because of its torpedo-shaped body and large fins.

Distribution
The Bala shark occurs in the
Mekong and Chao Phraya River basins, Malay Peninsula, Sumatra, and Borneo.[2]

Appearance and anatomy
These fish have a silver body with black margins on their
dorsal, caudal, anal, and pelvic fins. These fish can reach 35 centimetres (14 in).[2]

Habitat and ecology
Bala sharks are found in midwater depths in large and medium-sized rivers and lakes. They feed on
phytoplankton, but mostly on small crustaceans, rotifers, and insects and their larvae.[2]

In the aquarium
Bala sharks are popular aquarium fish.[3] Despite the common name "shark", these fish are generally peaceful and good companions to many other types of tropical fish.[3] However, the Bala shark is an omnivore and will eat other animals if they're small enough to fit in their mouths (including other smaller fish, and shrimp). Shrimp (ghost shrimp, krill, etc.) should have adequate hiding places to keep them from getting eaten. Bala sharks are widely available in most pet stores, but these fish may grow to a size too large for the home aquarium.[3]
They're hardy fish that will tolerate temperature changes, pH changes, and other factors to which other fish may be sensitive. The water pH should be 6.0–8.0. The preferable water hardness for this species is soft to medium (5.0–12.0 dGH). Water temperature should be kept between 22–28°C (72–82°F).[2] The Bala shark prefers be kept in groups of five or more specimens (although they can survive alone).[2] These fish require a covered aquarium as they are skilled jumpers.[3] Very young Bala sharks are sometimes kept in small aquaria. However, given their adult size, schooling behavior, and swimming speed, the fish quickly grow to need much more room. Hobbyists continue to debate over acceptable minimum tank sizes, but generally recommend at least a 6 feet tank. FishBase lists a minimum of 150 cm (5 ft).[2] Many believe the fish is simply too large and too active to be kept in commercial aquaria at all; only enormous, custom-built tanks are acceptable, if any tank at all is. Indoor ponds are also considered feasible housing options and may be better suited to the average aquarist. This fish's habitat is often destroyed, making these fish rare in the wild.

[edit] Conservation
B. melanopterus is listed as an
endangered species by the IUCN Red List.[1] It has become rare or extinct in many river basins of its native range.[2] In Danau Sentarum (Borneo), fishermen already reported in 1993 and 1995 that the populations have decreased dramatically after 1975, for no clear reason. Fishermen mentioned overfishing for the aquarium-fish trade or forest fires in 1975 and the resulting pollution as possible causes. The species is apparently extirpated in the Batang Hari basin (Sumatra) and it seems that all individuals of B. melanopterus exported from Indonesia and Thailand by the aquarium-fish trade are captive bred.[4]

http://en.wikipedia.org/wiki/Bala_shark

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