My concern would be that the angelfish would very much be dominated by the tang. I know it is an aggressive fish but it surely is one of the most beautiful fish available (should maybe be named Acanthurus pyxispandorae / Pandora’s Box Tang) and I would love to have it in my tank. Would it make sense/be ethical to maybe add some other fish (tangs/wrasses/anything annoying enough) to get the A. sohal’s attention away from the angelfish or would maybe the wrasse get most of his attention anyway (being striped horizontally like the tang and swimming around all the time)?