Cappuccino Bay has a 12" Vlamingi Tang which lept out of the water to grab a strand of grape calurpa!
However most of the smaller normally available tangs do not have the craving for mature plants and graze on the tips. Most cleanup crews likewise eat new growth but not the overgrown "too late" mature plants.
I have had the best luck with a soft & short spined sea urchin and sally lightfoot crabs. My pygmy angels and kole tangs did nothing.