Most people complain that they can't grow that crap! I picked up a rock about 6 months ago and noticed it had about 1 leaf on it. That 1 leaf didn't do anyhting for 3 months. Then Jeff came over hand helped me 'rescape' Next thing I know I come home from SoCal, and I have a halimeda bush! Mine is going tomorrow!!!
On a slightly different subject. We were talking to Mike about thinning the Kena tree forest in Shilo's tank. He said the only way to really get them out once established is to remove the rock from the tank, remove the tree and burn the area on the rock with a lighter where it was attached. Hopefully this will kill the root area. Maybe this technique would work with Halimeda? Just a thought.
Good luck, Scott