I found that my CBB went for aptasia when the volume of food was reduced. My 2 cents is to get him eating the foods you are providing like you are, let him settle in and worry about the aptasia control down the road.
In my tank whenever I walk up to it, my CBB and Midas Blenny both come over and stare up at the top of the tank. The other fish expect food will come, but those 2 stage themselves waiting for the magic of the "food falling from the sky". My CBB holds his own well with the others at feeding time now, but my fish population is pretty peaceful.
Good luck.
