Hey Keonigt,
Having kept both scleropages and osteoglossum, i would def recommend the silver. As someone else mentioned, jardini are very aggressive ( i have had them kill most tank mates). So i would get a silver instead, as you are gonna want to keep other things with your arowana eventually. As for converting them to dry foods, why is that so important? Variety is the spice of life with arowanas, why not just feed them loads of different frozen and live foods? In hawaii I bet there are loads of edible insects for you arowanas. I am a firm believer in live foods. But if you must i would put some size on you arowana first, them start by feeding soaked (expanded and soft) pellets, as rock hard pellets are alien to an arowana after weeks of eating nice soft bugs and fishes.
I also have to say that i have kept oscars and other large peaceful cichlids with arowanas - no problem, just make sure your arowana is significantly larger than the oscar. You can apply that principle to all arowana tankmates. Too big to be swallowed( by the arowana) and too small to swallow the arowana. Happy days
Best of luck mate, arowana are my absolute favs.
Guy