The plot thickens! Depending on the fish you have selected for the tank, this little object is revealed in the wireframe (at various sizes depending on the fish, which explains why certain fish will minimize/eliminate its visibility in rendered mode):
And as for the Powder Blue Tang, there's only one way that the banding can be demonstrated, and that's with a Photoshop mockup with the banding
smoothed out. Here's my shot at it:
And I agree that the Purple Tang has even more banding than the Powder Blue Tang. None of the other fish (maybe the Yellow Tang) have appreciable banding as they don't really have one large swath of color, but intricate details which require fewer smooth color changes.
