There are many suitable fish for a reef tank, before buying one do a little research, find out their diets and habits and decide if you can provide the proper home and whether your willing to tear your tank apart if it decides to nip at your corals. In my opinion there are no suitable angels for a reef. Many people keep a Copperbanded butterfly or a Raccoon in theirs to keep aiptasias in check. I find it easier move the rock to a tank where they live and let them take care of it. Of the two I find the copperbanded to be more acceptable.
Many people also keep dwarf angel fish in their reef.
One flame angel may never nip at corals while the next loves them. You may also have one in your tank for years who suddenly develops a taste for corals, and might wipe out an entire colony before you notice it. One final note before my list of suitable fish. But a clown without an anemone may cruise from coral to coral seeking a host, disturbing the corals and causing them to close. They also may pass slime from one coral to another causing further problems.