The smallest captive size arowana species are the Asian (Scleropages formosus) arowana's which rarely exceed 2 feet in captivity, however they are the most expensive and are illegal in some countries including North America.
Next are the Australian (Scleropages jardini and leichtardti) arowana's which like the asian arowana's only grow to around 2 feet in captivity but have a heavier body build, these are highly aggressive and adults will rarely tollerate any tankmates.
Black and silver arowana's (Osteoglossum bicirrhossum and ferreirai) both have a potential adult size of around 4 feet but usually stay slightly smaller in captivity with blacks usually only attaining around 2 feet in most cases, both have very rapid growth rates and will need a large tank from the start.
No arowana should be kept in a tank smaller than 180 gallons (6x2x2) and every effort to provide a larger tank should be made, ideally they should be kept in a tank that is a minimum of 4 times their length long by 2 times their length wide. Arowana's are not difficult to keep provided you supply them with the right foods and keep the water clean at all times with regular large water changes.
