Just a thought, but if the hardness of the pellets is putting him off (happens sometimes with a picky fish you're trying to get on pellets) but he eats krill, you might be able to get him to eat a soft krill based pellet. Some soft pellets I know of... HBH has a soft krill pellet, YFS has a soft carnivore pellet, but krill is down on the ingredients list, New Era has a soft cichlid pellet including krill, squid, shrimp, though fish meal is the first ingredient and I can't say I like cornstarch as the second ingredient in a fish food formula.
Only one of those I've actually used is the HBH which my fish liked. Not to start a food brand debate, but I've had picky fish in the past that wouldn't eat Hikari pellets and had no problem with NLS, Omega One, HBH, etc. I've had a few arowana in the past, no problem getting them to eat pellets, but they were smaller when I first got them, more in the range of 3-5 inches.
Edit-- somehow missed where it looks like you got him eating pellets... so ignore the above if it's superfluous.
But, imo if he's just starting to eat pellets I'd give him a while before introducing treats. Let him get more habituated first... Back when I had arowana their primary food was pellets (or flake), occasional live brine shrimp, but they were healthy and grew well... and back then commercial fish foods probably weren't as good as some of those today.
