Best filler corals?

[MeanGreenStompa]

So many easy corals carry the warning that they will swamp and overcome any nearby corals and should be kept on their own islands.

Are there any that instead will just peaceably fill available space and not kill off their neighbors?

 

[Cthulukelele]

A lot of the plague corals are pretty peaceful but just fill space more quickly than everything else. Discosoma mushrooms grow out super quickly while also being pretty friendly