I don't doubt what you say Minh, or your own experience, but how many specimens have passed through your hands? In several decades of experience, including working at a wholesaler and a retailer, and seeing hundreds of them deteriorate, I know differently. I can keep it as well providing I start out with a healthy, non-cyanide caught specimen, as can other experienced hobbyists. That doesn't mean I think it should be collected and imported. In my opinion, not enough of them survive capture to warrant their inclusion in the hobby in general, and relative to other species, it doesn't adapt to a glass box for MOST hobbyists nearly as readily. It's immune response is compromised much quicker for one thing, it's much more prone to C. irritans infections, and you can't tell me that a powder blue is in the same category of hardiness as a Zebrasoma or a Naso.
Now, purchase 40 Powder Blues, 40 Yellow Tangs, 40 Naso Tangs, and 40 Hippo tangs, watch your results, then repeat your above post to me. :wink:
I realize it can be kept by an experienced hobbiests in a large reef tank, with a bit of luck in seleccting a clean specimen, but that doesn't change how many others perish compared to other species available. No, it's not in Moorish Idol territory, but still in the realm of better left alone if you think the cruel side of this hobby, which we don't talk much about, should be mitigated.
I respect your own experience Minh, and you as a hobbiest in droves...however regarding this species there's too much empirical data otherwise to call it a hardy fish, despite the few that thrive for you or a handful of others here.
Peace
Jim