I have a bunch of caulerpa in my fuge. I would just keep the lights on the fuge for 24/7 and it shouldn't go sexual. They'll start going sexual if you put them on a 12on/12off light cycle. When it goes sexual it releases gametes into the water to fertilize and begin growing elsewhere. When it does this, the macroalgae turns all white and falls apart and dies. It is a last ditch effort to continue its species. It'll also do that if there no more nutrients to support it so much (that's why you trim it back), and it could do this with a large temp drop. This is all just what I've read about it before I put it into my sump...
Cheato smells and traps detritus. Go against the grain and choose caulerpa!
125 gal. reef w sump/refugium & 8-bulb 640w T5's
45 gal fresh w/plants + CPF lighting