Isn't Miracle Mud supposed to be sand with a few extra metals in it? I don't know about the overall effectiveness of it, some people seem to be very happy with it though (I understand the controversy surrounding the issue) ... so I guess a person could probably add the iron to make their algaes very happy. With that all said, I've never had a problem growing caulerpa, it grows jussst fine as it is, without any effort on my part to add iron or whatever.
PS. I found the smiley somewhere at
www.mysmilies.com. I used to have a bookmark for "Jabot Smilies" (I think it was a link that EmilyB had found), but, that page no longer exists. So, smiley-less, I had to search for an alternative. Basically I just did a search on "smilies" and went to one of the first pages I turned up. There were a lot of pages found under that search criterion...