The armatus will take non live when it wants to. The aro may help him to get non live food, but it's not a guarantee thing.
I used semi frozen shrimp or krill, it doens't sink right away and it gets them interested.
Also, try to throw the food over the tank rather than just dropping it in. Most fish are trained to look up for food.
It won't happen the firts time. If they go after it then turn away, you're on the right track. it takes persistence to get it done.
They'll start to go after it then back off, then they start to swallow it then spit it back out and evnetually they'll take it every single time. I have mine eating pellets already.
Dither will help, but armatus aren't like most fish...they're stubborn in their own way.
stan