I just read somthing that says their the bully of the corals...I would think placeing one next to the other would end up in death. You could place them close, but don't risk putting them right next to eachother.
they will try to kill each other ending either both or 1 dieng just make sure there 'wpeer' tentacles canot reach each other perosnally i would put one,one side of the tank and the other the other side