You could try to put them in timeout, remove them from the tank, add the new addition, then add them back in. Wouldnt hurt to move the tank around a bit too, make it seem like "new" home.
I know stuff like that can work with freshwater fish so I dont see why it wouldnt work with saltwater.
40Gal Planted- 10Gal RCS Planted
6 Julii corys, 1m Furcata Rainbows, 2f 1m Bose Rainbow, 2 mystery snail