Dacia, the royal gramma is likely to set up a territory of it's own. They may also hide a lot when first introduced to a tank. They tend to like to hide in crevices and bolt into a "hole" for sleeping. They are aggressive to other fish entering their territory and tend to posture and open their mouths really wide in an aggressive stance. I think of them as darters, always darting in and out of the rocks and holes in their area. I loved watching mine. Sometimes I'd be looking at the tank and notice a purple head sticking out of a hole. Very cool fish but, quite possibly would harrass the more timid firefish.
The maroon clown is arguably the most aggressive of the clown fish. They tend to stake out their territory and are usually not afraid to attack any fish daring to enter their domain.
HTH