One trick is to make sure you grab the base of the plant, otherwise you're just pruning.
I introduced a bunch of the stuff to a tank that I maintain in my companies entrance lobby about a year or so ago. It had pretty much carpeted the tank bottom, and actually buffered the sandbed against the inevitable falling powerhead when I wasn't around. About 3 weeks ago I introduced a hawaiian saifin tang, and all I can say is that he's got a real apetite for the stuff. He's munched his way through half of it. I've started hanging nori in a veggie clip in the hope he doesn't devour all of the halimeda.
I have 3 hawaiians at home in different systems too, and I use them as something of a cleaning service. Whenever I see a piece of stray macro I don't want on a piece of rock, I just put it in the tank, and it's clean as a whistle in a few hours. The only green plant matter I can honestly say they don't care for is bryopsis. I have a flat red ribbon macro that grows super slow, and they don't touch that either.