Those are beautiful shots of picture, but i must say that it is possible to have silver arowana with discus. But you really need to plan this move at an early stage when they are young.
At the moment i have a 6 ft x 2 ft x 2ft fresh water tank which house a silver aro, 5 clown loachs, 4 bala sharks, 1 sailfin pelco, 1 albino pelco, 2 red melon discus, 1 bumble bee catfish and a few more neon tetra left in the tank.
i had no problems with them over food. Just make sure everyone is fed and yet again this method of mine is still an experiment. I won;t know what will happen when silver aro hits the 1 foot lenght.