No problem OP, I own 5 Asian Arowanas in a 522 currently. But ultimately it boils down to what type of arowanas you would like to keep.
Silvers or Afro will grow really long, so 522 ain't your best bet. Asian Arowanas such as Red Tail Golden and Super Reds can be kept in a 522 for a long long time if you are planning for 1 piece or so only. For a comm tank, 522 can only keep smaller variant such as CrossBacks, as they rarely grows up to 2ft length even in farms kept for breeding purposes.
I think you should focus on the health of the Arowana in your tank (etc filtration) instead of the tank size. Many people in Asia managed to keep healthy Arowana in tank size like yours, or even smaller such as a 422.