I never feed my feather duster, I just let him eat the extra stuff left over in the water column from feeding the other fish, and Its doing great, I've had it about 6 months and its already grown and extra 2 inchs of tubing.
Funny thing is I used to feed frozen food, and silversides to the corals and fish in my tank, but due to an algae break out, I cut bake on feeding and only feed dry pellets to my fish and feed nothing else.
Everything is doing just as good as it normally does, if not better. especially the feather duster. (most of my growth for my feather duster has been during the time I have only been feeding dry pellets to my fish, which has been about 4 months)