Pangasianodon gigas

Native to the lower Mekong river running through parts of China, Thailand, Laos, Cambodia and Vietnam.

It's a pelagic species inhabiting main river channels and larger tributaries.

Totally unsuitable for home aquaria. It's a very active open water species and tends to be skittish when kept in cramped conditions. This can lead to problems with the fish banging into the tank glass and items of decor, often resulting in injury. It's beyond the limits of most public aquaria to house one of these long-term.

Temperature: 20 – 28 °C68 – 82 °F

pH: 6.5 to 7.5

Hardness: As the species' natural waters are subject to annual flooding, water parameters can vary considerably over the course of each year. General hardness is thus not critical, and anywhere in the range 2-30°H would be acceptable.

Primarily a herbivore, but also feeds on smaller fish and crustaceans.

Mature females are likely to be rounder-bellied than males.

In nature it's a migratory species, moving upstream to spawn during the late spring and summer months. Unsurprisingly it hasn't been spawned in an aquarium, but has been bred in large numbers on fish farms. Dedicated breeding programmes exist in some of its native countries, aimed at restoring wild stocks. In Thailand some 10,000 captive bred fish have been reintroduced to natural waters in a project co-ordinated by the Thai Department of Fisheries.

Pangasianodon is separated from other pangasiid generea primarily on the basis of some morphological differences including a lack of teeth and massively reduced barbels in adult specimens.

Sadly it's numbers are declining rapidly in nature, through a combination of unsustainable fisheries, damming and habitat destruction. Since 1990 wild stocks are thought to have undergone a decrease of over 80%. From an annual catch of over 60 specimens in 1990, only 8-11 were being caught per year in the early part of the 21st century. More recent studies have shown that the existing population has retained much of its genetic diversity, so there is at least a chance of recovery.

It's been listed as "critically endangered" on the IUCN Red List of Threatened Species since 2003, and will almost certainly remain there for the forseeable future. International trade is also banned (it's included in Appendix I of CITES), so you're unlikely to see it on sale anywhere.

It's fair to say that this is one species that shouldn't be considered an aquarium subject under any circumstance. If this seems a touch extreme consider that not only is it on the brink of extinction, but it's perhaps the biggest freshwater fish species in the world. How can anyone hope to provide the conditions required by such a beast in their home?

Unfortunately related species such as Pangasius hypophthalmus and Pangasius sanitwongsei are widely available in the hobby. Whilst not quite as big as P. gigas these also grow huge and make equally unsuitable aquarium inhabitants.

In 2005 and 2006 a collaborative project funded by the Darwin Project, entitled "Development of a conservation strategy for the critically endangered Mekong giant catfish" was carried out, as no overall plan for saving the species currently exists. The results are yet to be published, but it's to be hoped that the organisations involved are successful in outlining an effective, sustainable conservation strategy for this giant among catfish.