I agree with Mike. I have found that marine fishes, for the most part, are FAR too intelligent to fall for the old "Let's just rearrange his room and fool him!" trick. In fact, I've never had one fall for that trick, they have to be removed, two week time-out was the minimum that worked, once. Basically, you could put the angel into a QT (or your sump if you have it set up that way), physically separate them, allow the tang time to establish a territory and get its sea-legs. Then, reintroduce the angel and, if it's been given sufficient time to "feel" as though it's a newcomer again, should mind its P's & Q's a little better.
However, I caution a bit against this instead in favor of giving them more time, because I have never seen a territorial angelfish do what a territorial tang can do. It is not a pretty sight.
