While South America has two Osteoglossum arowanas (the Silver arowana and the Black arowana), and Asia and Australasia have three Scleropages, Africa has a single species — Heterotis niloticus.
The feeding mode it uses varies according to its age and what habitat it is living in. Little ones, measuring 10-20cm/4-8” long, shift from feeding on small aquatic invertebrates, such as Daphnia, to seeds and detritus.
When they’re found in lakes, they start feeding on detritus when they hit 30-40cm/12-16” long, but when they’re found in rivers they don’t become detritivorous until they’re nearly 0.6m/2’ in length.
They’re rarely kept in the aquarium and have a reputation for being difficult to feed. I’ve tried to rear 3cm/1.1” juveniles before and been wholly unsuccessful.
They also tend to arrive from Africa in a somewhat emaciated state and often riddled with parasites. They’re challenging fish and for that reason are best avoided. There are some little ones on sale in the UK for around £120 apiece.
This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.