Matt Clarke on an arowana which has been imported from the Colombia-Venezuela border.
Common name: Blue arowana
Scientific name: Osteoglossum cf. ferreirai
Origin: This fish was captured on the Colombia-Venezuela border, in the same region as Uaru fernandezyepezi.
Size: Up to 120cm/4', but 90cm/36" is considered large in captivity. Arowana, particularly the more common Silver arowana, are a popular food fish and I saw many on sale at the local fish markets of Manaus, Brazil, most of which measured about 100cm/39".
Diet: Arowana are surface-dwelling omnivores. Stomach content analyses of wild fish have shown that they feed on spiders, beetles, grasshoppers, terrestrial insects, plants and fish. In captivity, they'll do well on cichlid pellets and chunks of defrosted frozen fish.
Water: Ideally neutral or slightly soft and acidic, but fairly adaptable in captivity. It's usually not a problem to keep them in harder water.
Aquarium: These peaceful fish mix well with other large fish, but need very big tanks with lots of free-swimming room. A 183 x 61 x 61cm/6' x 2' x 2' tank should be the minimum, but longer and wider is better. Apart from their size, they're easy to keep and become tame enough to feed from your hand. Install an oversized filtration system to handle the high ammonia wastes. Don't keep them with anything small (they'll eat them) or anything too aggressive (the arowana will get injured or will jump out, potentially smashing any cover glasses).
Notes: There are only two species: the Black arowana, Osteoglossum ferreirai, which comes from the Rio Negro and its tributaries in Brazil, and the Silver arowana, O. bicirrhosum, which is more widespread. O. ferreirai is rarely seen in the trade, especially at larger sizes. O. bicirrhosum is currently only recorded reliably from Brazil, French Guiana and Peru.
This species was originally believed by the supplier to be a sub-species or a geographic variant of O. bicirrhosum. O. cf. bicirrhosum (cf means conferre - and is Latin for "compare to") appears to have slightly different colour, especially on the dorsal and anal fins, which are predominantly blue with a pink edge. The squiggles in the fins of Arowana usually seen in Manaus are different. However, it may in fact be more closely related to O. ferreirai, or most likely the same fish.
Museum records show fish only from the Rio Negro, Rio Branco and Rio Unini (a Negro tributary) in Brazil. The records I have checked list no Osteoglossum species in the waters of Venezuela or Colombia, so even if this is simply ferreirai, it represents a new occurrence for the species for this region.
A couple of trade experts have recently told me that they've compared this form to sub-adult Black arowana, side-by-side, and the two fish appear to be different, so these may indeed be a race of the Black arowana.
Others completely disagree and say that these are nothing other than juvenile Black arowana that have been given a different name by the exporter in South America to make them sound more interesting, and inrease their price on the market. It certainly seems unlikely that it is a distinct species as some in the UK trade have been claiming.
Availability: At the time of original publication, this fish, on sale at Fish Trek in Ashington, Northumberland (01670 851160), was the only specimen in the country. It's now been sold. The species was imported by Tom Halvorsen Ltd (07977 098127). In November 2004 a new shipment of these fish arrived in the UK.
Price: On sale for 195.
This article was first published in the November 2004 issue of Practical Fishkeeping magazine.