Family
Cyprinidae
Distribution
Work by Ng and Kottelat published in 2007 confirmed that contrary to much of the published information this species does not occur in Indochina and is restricted to Borneo, Sumatra and possibly Peninsular Malaysia. The full extent of its current distribution is unclear as many populations have dwindled in numbers or even vanished completely over the last few decades. For example it is now thought to be extirpated from the Batang Hari river drainage, Sumatra and in the Danau Sentarum National Park, Borneo it has been declining steadily since 1975. The precise reason for this deterioration has not been well-studied although over-collection for the aquarium trade and pollution of waters due to forest fires have been mooted. Since 1996 it has been listed on the IUCN Red List of Threatened Species under the ‘Endangered’ category, and as a result it is almost certain that wild fish are unavailable in the aquatic trade with 100% of those seen on sale likely to originate from commercial farms in Thailand and other countries.
Habitat
It is a pelagic species primarily occuring in rivers but also some lakes such as the Danau Sentarum system.
Maximum Standard Length
Fully grown at 13.8″/35cm and IS capable of achieving this size in aquaria when properly cared for.
Minimum Tank Size
This is a very active fish and a tank measuring 96″ x 24″ x 24″/240cm x 60cm x 60cm/906 litres should be the smallest considered to house a group of adults.
Tank Setup
Choice of decor is not as critical as water quality and the amount of open swimming-space provided; we’ve seen very healthy-looking specimens being maintained in completely bare set-ups for example. However should you possess the means to both provide and decorate a sufficiently-sized tank for long term care this species would look superb in a set-up designed to resemble a fast-flowing river with a substrate of variably-sized rocks and gravel, some large water-worn boulders and perhaps a couple of driftwood branches. A giant rivertank manifold could even be constructed to provide naturalistic unidirectional flow.
Like many other species that hail from running waters it is quite intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive. It also does best if there is a high level of dissolved oxygen and a decent level of water movement in the tank. Even if a rivertank manifold is installed an enormous external-style filter or two are going to be needed in order to provide the desired levels of oxygen, flow and surface area for bacterial colonisation. Be sure to fit the tank with a heavy, tightly-fitting cover as it can be quite skittish at times and has a powerful leap.
Temperature
72 – 82°F/22 – 28°C
pH Range
Happy within the range 6.0 – 8.0 but a value close to neutral is usually recommended.
Hardness
5 – 15°H
Diet
Like many cyprinids Balantiocheilos melanopterus is omnivorous and something of an opportunist with stomach analyses of wild specimens revealing it to feed on insects, crustaceans, algae and other plant matter. In the aquarium it’s just as easily-fed and will accept just about anything offered. For it to develop its best colours and condition offer regular meals of small live and frozen foods such as bloodworm, Daphnia and Artemia along with good quality dried flakes, granules and plenty of vegetable matter. Shelled peas, blanched courgette, spinach and chopped fruit all make good additions to the menu. Larger specimens will also take chopped earthworm, prawn, mussel etc.
Compatibility
Given its potential size this species is clearly unsuitable for the general community aquarium. Though normally quite peaceful it will also eat very small fish and can upset slow-moving/shy tankmates with its constant activity and vigorous feeding behaviour. It is therefore only appropriate for very large tanks containing robust, similarly-sized tankmates that enjoy the same conditions. There are a number of suitable choices but recommendations include Hypsibarbus wetmorei, Barilius, Cyclocheilichthys, Osteochilus, Barbonymus, Mystacoleucus and larger Garra species.
Although it is gregarious by nature it is a shoaling rather than schooling species which develops a distinct pecking order and therefore should always be maintained in a group of five or more. If only two or three are purchased the subdominant fish may be bullied incessantly whereas solitary specimens can become aggressive towards similar-looking species.
Sexual Dimorphism
Sexually mature females are noticeably thicker-bodied than males but it is impossible to accurately sex young fish.
Breeding
As far as we know it has not been bred in aquaria although it is farmed for the trade in large numbers via the use of hormones.
Notes
This species may also be seen on sale under the trade names ‘Bala shark’ or ‘tricolor shark minnow’ and is one of the commonest fish to be found in aquatic stores. Unfortunately it is almost universally offered for sale as a juvenile (usually around 2 – 3″/5 – 7.5cm) with little to no information regarding its eventual size. Long term care is simply beyond the resources of most hobbyists and while it is undoubtedly a stunning aquarium fish we strongly recommend you avoid it if you are unable to provide adequate, sustainable conditions. Most shop-owners will tell you that silver sharks are among the species most often returned having outgrown their tank and many are reluctant to accept them as the resale value is very low. We dread to think how many end up spending drastically shortened lives in cramped surroundings.
The genus Balantiocheilos was considered monotypic for well over 150 years with Balantiocheilos melanopterus the sole represenatative. However in 2007 Ng and Kottelat described B. ambusticauda from the lower and middle Chao Phraya and Mekong drainages in Thailand, a result of the authors comparing previously collected specimens of Balantiocheilos from Thailand, Sumatra and Borneo to each other rather than discovery of the new species in nature. The holotype of B. ambusticauda was collected from the freshwater swamp Bueng Boraphet, Nakhon Sawan province, central Thailand in 1967, for example. In the paper it was stated that:
“Balantiocheilos ambusticauda is distinguished from its sole congener, Balantiocheilos melanopterus, in having a shorter snout (27.5–33.9% HL vs. 33.2–39.1) that is rounded (vs. obliquely truncate) in specimens larger than ca. 80 mm SL, posteriorly directed groove at rictus curved (vs. straight), and narrower black margins on the pelvic and anal fins (on distal third of both fins or less vs. on distal half or more, with pelvic fins sometimes entirely black).”
In the few colour images that exist it appears to possess golden colouration on the head and dorsal surface of the body which further separate it from the uniformly silver Balantiocheilos melanopterus. It is also a smaller species with a maximum length of around 8″/20cm, this having been previously noted by several authors including Rainboth in his 1996 book ‘Fishes of the Cambodian Mekong’ (but referring to what were then thought of as Indonesian vs. Thai/Cambodian populations of Balantiocheilos melanopterus).
Originally B. ambusticauda would have ranged between Bangkok and the lower Nan river in the Chao Phraya basin and from Vietnam and Tonlé Sap lake, Cambodia as far as the lower Nam Ngum river, Laos in the Mekong drainage. However Rainboth only found it in a handful of small rivers at the eastern end of Tonlé Sap whereas in the 1950s it had been abundant in rivers downstream of the lake. We have been unable to find any records for Cambodia post-1996 and it is almost certainly extirpated from Thailand where the last specimen was recorded in 1986. Ng and Kottelat surmise that the species may well be extinct in nature although more recent records from Vietnam still require ratification. There is no evidence to confirm reports that overfishing for the aquarium trade is to blame for this demise and it seems more reasonable to assume that Balantiochielos species are simply ill-equipped to cope with large-scale environmental change such as the damming of rivers.