Well there are lots of problems out there trying to id algae especially caulerpa. Caulerpa J.V.Lamouroux, 1809: 332 :: Algaebase
Scroll down on that page and look at all the different type of caulerpa there are and also look at how many types of Racemosa there are too.
Main problem is most hobby id sites actually have allot of the algae wrong. They basically take alll the caulerpa that looks similar and throw it under about 8 different names if that. kind of like there are a ton of montipora we call capicornas which are not.
What makes me think it is Bikinensis is the flat tops where racemora is more round.
Well, as they say, great minds think alike. I was contemplating the round verse flat also, but there is a C. Racemosa with the flat tops also. Also another consideration I had was the stalk-like C. racemosa vs. the creeping vine-like C. bikinensis.