Hey guys, I've just read this about Southdown sand from http://reefkeeping.com/issues/2005-04/totm/index.php
"Initially, I included a 2" to 3" deep sandbed consisting entirely of Southdown play sand. What a mistake that was! I have been trying to get rid of all that sand for quite some time now. While it may have served a purpose for the first year or so, all it has done lately is cause lots of headaches. I've found that the Southdown sand kills the edges on many of my Echinophyllia and significantly retards their growth. The next tank will have a bare bottom with a faux sandbed (using Starboard on the bottom). Until then I'll continue to try to remove the Southdown and replace it with a thin layer of crushed coral. I dont know if thats any help or affects you at all?