Hi, I fed mine with hikari jumbo stick as well. My experiences as follows:
1. My arowanas are considered juveniles at around 8 to 9 inches.
2. They were fed worms at the fish farm. But prior to the collection, they starved it for 3 days.
3. 4 of the arowanas took to eating the hikari jumbo carnistick immediately. But i noticed 1 did not. It would hold it in his mouth and then spit it out.
4. It kept doing this for a week. After maybe at the 8 or 9 day mark, i noticed that it finally started to eat one pellet that had been floating in the water for awhile. The rest had already had their filled. I always threw one or two more in to entice the last stubborn one.
5. From that day onwards, I would have a small container with tank water and I would let the hikari soak in it for about 10 to 15 seconds. once it becomes soft, I would then throw it in. I don't have any problems feeding all 5. Last night, I just soaked it with dewormer medication and they still devour the pellets.
6. I also break the hikari sticks into 2 or 3 pieces for mine. I believe the hikari stick could be abit too big for your 6 inch aro. So you will need to break it into smaller ones.
I think the key message is to be patient. The temptation to do additional actions such as adding fishes etc is very tempting especially when we are new. We are all anxious. I would encourage you to be abit more patient and give it more time. They will be ok without food for a much longer time. Also you mentioned that your arowana is only 6 inches... which means that you have only recently received it? If so, give it another week or so before you consider adding more fishes. Because adding new fishes introduce more variables which we have to control and manage.
Since your aro is still small, converting it into eating pellets would be quite useful in the long run. I also understand from the farm that for small aros, they may feed up to 2 to 3 times a day. When I first received mine, they would eat only about 3 to 4 pellets (full size) twice a day. But after a month, they are eating about 6 to 10 pellets once a day on weekdays. And then twice a day on weekends (since I am at home). For water change day, I don't feed them for at least 12 to 18 hours until I perform 30% water change.
And just to add, whenever i feed it twice a day, each feed is about 80% of what i give compared to the days when I feed once a day. Under feed a little is better than over fed.