I'm a totally BTA newbie, but this is what happened in my tank. Tank-raised Maroon would only eat pellets until BTA was introduced. At first my Maroon was so excited about the BTA and put any and all food into it (whether to feed or to store, who knows).
I've had the BTA over a week now and my Maroon eats most of the food itself, but puts what it doesn't like in the BTA (i.e., likes=mysis shrimp, doesn't like=krill, silverslides, formula2, etc.. Regardless, the BTA doesn't appear hungry at all because I've tried to feed it about a million things and I end up having to take them all out. Thus, whatever relationship they have the seem to be pretty happy with it.