You can mix them but caulerpa can go sexual if t is exposed to a day and night cycle. I have had a mixed experience with caulerpa going sexual as it is a good food source for corals. I think the variety of caulerpa that is being kept can also make a big difference. I have been sticking more to red macros and chaeto in my last refugium. When I get my new system up and running I am not sure what types of macro algae will be introduced but I might keep some caulerpa again because of the water volume in the system.