The platability of Caulerpa varies, and it's hard to predict what may eat a particular specie, or variety of specie. My Diadema urchin grazed Caulerpa incidentally, but didn't seek it out like some other macros. I've kept a "lawnmower" blenny, but not a Bi-color. The lawnmower didn't eat Caulerpa, and generally blennies are considered to be micro-algae grazers who may incidentally eat some of the more fragile filamentous algaes. My references all say that Centropyge angels may eat some Caulerpa, but can also pick at Tridacna and some corals to the point of recession/death.
A Diadema would control most alga your Zebrasoma tang may not. It can't pick out Caulerpa from between the branches of coral, though. And it will put the hurt on your coraline algae. I eventually had to get rid of my Diadema to attempt to grow seagrass.
I'm trying a Siganus Lo (Foxface Lo) rabbit fish in my tank. Siganus are supposed to eat a wider variety of macro algae than Zebrasoma, including some Caulerpa. At any rate, your Zebrasoma is less likely to attack the rabbitfish than a new surgeonfish, I think. I like the Foxface, it's right out in the open most of the time, and has a big appetite for algae. Mine is a small adult. But I haven't seen it grazing on the Caulerpa var. peltata in my tank so far...
