Arowana once large enough will snack on everything in that tank. So absolutely no way as people have mentioned before.
I would not add too many giant danios if I were you, you are at some point going ot have to up the numbers of cichlids considerably. Auratus if they both turn out to be male will fight each other to death, if it is a male and female, the male will kill the female unless you add about 7 more females. These fish (auratus) start showing major aggression at about 2 inches.
All mbuna except the very aggressive ones should be kept in a 1 male to 4 female ratio. This helps spread the aggression from the dominant male to several females when he is in spawning mode, anything less and it can lead to stressed or at worst dead females.
In a 55g tank, with cichlids alone, you would be looking at a maximum of 12-15 fish in the 3 species with correct male to female ratio. As I mentioned this technically means with the Auratus alone, you are going to be overstocked with just having the two of them. Labs are ok in 3's as they are not overly aggressive, can really depend on the nature of the fish as well, some are more aggressive than others, even though they are still on the very peaceful side of African Cichlids.