That is a huge toadstool.
A place that I used to work for had one that big in their 180 gallon display tank. The tank is actually one of the tanks featured in Michael Paletta's "Ultimate Marine Aquariums".
I would love to have a big frag of the toadstool, does anyone have big ones to sell? i have 120g and would love to have a big one in it.. anyone let me know. thanks so much kristin1422@yahoo.com e-mail me