I'm pretty sure at least some of my RES are eating pellets in my forage pond. I put feed out daily for the minnows in the pond and I think the RES got started eating it.
The reason I think so is I noticed when I wanted to catch some adults to move to my sediment pond to restock it, it was much easier to catch them if I fed the fish first and fed only in the area I wanted to fish. Caught 10 that way to transfer.
Here is a thread I keep up specific to RES. Browse through it and there are some links to feed training RES. I will also add this thread to the links.
RES info and links 
