From personal experience with IT dats, don't do it unless you have a large tank with a cave area for the dats to hide in. A solitary australasian arowana already in a tank has most likely claimed the whole tank as it's territory. The datnoids will tend to take lower part of the tank, and the arowana will want all the tank, which leads to problems. The arowana can be aggresive but will end up recieving a beating when up against a defensive datnoid.
My advice is if you do decide to try it, have a hiding spot for the dats, keep all fish well feed ,and keep good water conditions.
I currently house a banjar in an 260 gallon. . They are just like every other australasian arowana, depends on the individual fish. This particular fish doesn't like other large fish, but is fine with smaller fish that occupy the bottom part of the tank.