Have you actually tried live? Or are you just trying to get him on processed food from the get go?
Since it is wild - I would focus on getting him to get (anything) at this point - which he would eat in nature - and then, when he is established - start him on other foods.
Agreed on dimming the tank - lots of cover on top (floating plants, etc.) Don't forget that this is a fish that grew up wild, in a certain habitat. Try to match that to make him feel more comfortable, if you haven't already.