Arowana will eat pellets eventually. Also bare in mind that arowana are very finicky fish. It is possible if moved from one place to another they won't eat anything at all for a couple days simply because they are moody. Sometimes just putting them in there everyday at the same time and waiting to see if he eats them, then scooping them out again so as not to dirty the tank is what it takes to get them to eat. Eventually he will adjust to his new home and will eat when you put the pellets in because he is hungry and you were consistent. I had one fish with a similar personality go 5 days without eating anything. But by putting food in everyday at the same time, on the 6th day he ate the pellets and has been on them ever since.