Congratulations on your new baby, it's gorgeous
Wish you all the best
A varied diet is best for your Arowana: Shrimp, pieces of fish, pellets and their favourite is live insects... crickets, meal worms, earthworms are all good.
For now, feed her whatever she will eat as she is very small and you need to put some growth on her but start trying with other foods first... if she takes pellets, shrimp or fish, its great, if not, go with insects but keep trying to introduce the other foods as well and use insects as a treat ans to vary the diet.
Its nice when they take other foods from small and not just insects otherwise you often battle afterwards to get them to eat the other foods
Unfortunately as has been said, she will outgrow the 170 gallons very fast so if you can, go with a bigger tank so that in a year's time you dont have to upgrade again
Make sure your lids are closed tight and no gaps at all times.. they are masters at jumping.
Good luck and keep the updates coming