That's so fantastic that you have such growth. Aren't you loving this!
Remind me, are you using tap water or Reverse Osmosis purified water?
Don't worry about the Caulerpa melting away. Just keep it trimmed.
You can trim all that macroalgae back to manageable levels by hand or by fish. Tangs and Rabbitfish are excellent grazers of macroalgae, but may also completely wipe it out. Almost all algae is extremely beneficial to the reef aquarium.
That's why so many of us keep Refugiums, to have the benefit of algae growth where we can manage it rather than see it disappear into the belly of a fish. Now that you are having success with your tank, you may want to consider upgrading to a larger tank with refugium or add a refugium to the existing setup.
As usual, we are here to help you with the process.
You did it before. To download a pic, press the button with the camera
and arrow.