Zebrasoma flavescens would be my choice. They don't seem as skittish as their other cousins, and Alice has already brought up the consideration of fish size. Having said that, if Caulerpa control is the only reason for getting a tang, you could just as easily pull out the stuff every two weeks --by hand.
There are far less delicate fish than tangs to keep --but if you're getting a tang because you just gotta have them, hey more power to you.
A tang spooks easily perhaps because as a reef tenant (juvenile and younger), the territory it patrols can reach several hundred square feet, and a typical cramped reef tank can drive some of them batty. Excessive stress of most sorts lowers fish resistance to germs or parasites in the tank.
Tangs as a group do include some of the most graceful, beautiful, and interesting fishes, though.
HTH and if you settle on one fish and have questions, don't hesitate to bother Alice.
Or Doug. Or Steven. Or...
[This message has been edited by horge (edited 08-13-2000).]