I hope you find one. All my tangs eat any and all algae it seems(except cyano but including diatoms, hair, all macros I have used etc.) I do believe that many of the tangs learned this behavior from my sailfin which was one of my first fish in the tank. My powder brown also seemed to like the algae over the frozen when I first put it in.

Another thing you could do to help them learn this behavior is to cut back on the feedings some.