Haven't heard of any successful breeding of these arowana outside its original country. In those countries also farm breeding taking place in a sophisticated, controlled environment, in large ponds. They says it's very difficult to breed these species, even after breeding, successful spawn is further less, and that is why the prices are up that much. There are some YouTube videos available, just watch it.
I have also heard that most of these farms do some 'treatment' to the fish so that they don't breed outside, which will affect their business. However I am not sure if it's true or not.
From what I know there is no point wasting you time for attempt to breed, in an aquarium.
Just keep them, watch them and enjoy the beauty.