i have tried to get a caulerpa strand growing in mymain tank for about two years now, and as soon as i get it in there the three tangs mow it down. This was with the feather caulerpa. However they wont touch the grape caulerpa, and now its growing like weeds in the main tank. I have three tangs, purple, yellow, and hippo, and a lawnmower blenny, and tons of snails and the stuff keeps on growing!
good luck!
jon