I have now dived on some of these Red Sea reefs (lat 27.858° long 35.331°) and they are NOT staghorn, in fact they consist of massive and encrusting corals. So, feeling I am back to square one and don't really understand this system at all (not such a bad feeling, although I don't like having published misinformation). DB

correction to this paragraph: "..the foundations of most reefs have been exposed to at least 100,000 years of weathering during glacial periods.." DB