I think the OP has just gone and threw himself off a cliff!
The arowana, although not my cup of tea at all, is arguably the king of aquarium fish. Even I can't deny how majestic it is. Unfortunately it's a victim of its own beauty. Many hobbyists, sadly many of them young and inexperienced, just have to have this fish, but simply can't house them for life in the size of aquariums they require.
So you get people putting them in tanks that are too small and then argue until they're blue in the face that, in their opinion, they are doing the right thing by the fish because the fish is swimming ok, or it's eating ok. Is that really enough justification? Oh, and then they'll come out with the, "well it seems happy" line, which bewilders me.
For what it's worth i think some fish just deserve more than the bare minimum of what we can offer them and the majestic arowana is right up there.
If you come up with a genuine generous tank size for an arowana, then double it, then maybe, just maybe you might sort of be in the right ball park, arguably.