INdeed caulerpa can be purchased at most local fish stores. there are dozens of different types of caulerpa out there so do a little shopping for them look around even get a book pick out one then see if you can find it anywhere.. one place to go to find caulerpa is <a href="http://www.inlandaquatics.com" target="_blank">www.inlandaquatics.com</a> go to the products section.. this is my place of employment we do a lot of nation wide delivery and a lot of caulerpa. i'd check it out.. but always try your LFS first you never know..
Brian