If you are new to fish keeping, DO NOT GET AN AROWANA.
They are not a fish for beginners and should not even be for sale because they get too big for the average aquarium. Adult Arowana need a pond at least 20 foot long x 10 foot wide x 3 foot deep, or bigger.
I am not going into their food because I don't think you or anyone else should be keeping them. I'm sorry if that sounds like I'm being a bastard, but they are big fish that don't belong in tanks, and people shouldn't even contemplate keeping them unless they have had some previous fish keeping experience, and you have a huge pond for them to live in.