"Scientists first detected Caulerpa brachypus in the southern IRL in 2003. Initial concerns that the alga would gain a foothold and quickly spread through the IRL have been partially allayed with the finding that it is largely intolerant of the high-light conditions characteristic of the shallow IRL system (Brian LaPointe, personal communication).
Salinity tolerance limits for Caulerpa brachypus appear as yet undetermined, although C. racemosa has been demonstrated to cease growing if salinity is reduced to 20 ppt and C. taxifolia is killed outright when salinity is reduced below 10 ppt (Carruthers et al. 1993, ANSTF 2004).
In Florida there are few if any herbivores that readily consume this alga, though the reasons for this are not entirely clear. Preliminary evidence from studies on the coast of Florida suggests that the defensive compound caulerpenyne may not be present in sufficient quantities in Caulerpa brachypus to deter grazing by generalist herbivores (e.g., parrotfish), but that the chemical may still be important as an activated defense compound (Lapointe and Yentsch 2003)."
Not sure what kind of tank you have, but depending on your live-stock, you may want to, temporarily, greatly increase the lighting and/or use hyposalinity. Decreasing feedings, using GFO and continued manual removal are all sure to help.