My RB pacus occassionally get monkey chow, dog treats and cat treats (if there's vegetable matter in them.
You're right on about panaques putting out a lot of waste. I solved that problem by using a bead filter rated to 1200gals with fish as opposed to using a filter rated only for the 300gal size of the tank. An added bonus is this filter has a backwash capability which I put to good use once a week. I use a pool pre-filter leaf screen to catch the major portion of ground up driftwood my panaque chews up. It always looks like yesterdays coffee grounds in that screen box.