How does a yellow tang "attack"

[Madreefer]

My yellow tang does that to both my foxface and a naso tang once in a while. I've watched closely and he does'nt really poke that spike out too much and just letting them know who's boss. I've only seen 1 cut on my naso in 3 years. Most of the time they all seem to be buddies. They are called surgeonfish I think because of the spikes on the sides.