That is some great info!
I agree, Predatory fish can go a long time without eating. Most people overfeed there fish as well, especially Oscars and Red Tail Cats. I once read a document which stated these type of 'glutton' fish only eat 2-3 times a week in the wild.
I 'accidently' fasted a 8" texas cichlid for almost 5 weeks. I forgot I had him! (I know, I'm bad, this was a long time ago)..
Arowanas fast themselves in the wild on purpose, from what I understand..
Have you tried using a hunger enticer? In order to get my lionfish to eat prepared food, I would often soak their goldfish in a Garlic Extract (Garlic XTREME by Kent), then once they recognized me as a food source, I began to soak krill in garlic as well. I would put it on a feeding stick, and wave it in front of it's face.
Does the Dat have competition for food? I noticed this will always make fish try a new diet, because they don't want to loss the food to the competition in the tank.
Maybe go from Live Food, to Frozen meaty foods, then to Pellets.. The transition should be easier. Most fish that 'suck in' their prey, such as the Lionfish, have a hard time going for pellets. I still have yet to get my Lionfish to eat pellets, but they will eat krill off the top of the water.
Hope that helps!
Miles