Some macroalgae species, especially fast-growing ones like some Caulerpa live algae species need regular trimming, which is as well perfect to effectively remove the nutrients from the tank.
Other macroalgae, especially red macroalgae species grow often more slowly and need rarely atrimming.  

When green macroalgae species turn white oy yellowish, or lose their structure and turn "mushy" they should be removed / cut off to avoid nutrients getting back into the aquarium.