My 5" yellow is a brute, but mostly only to new fish, and sick fish. He'll playfully chase at other fish.
Had an anthias that got injured, then an infection set it - the tang kept smashing its tail into it.
He was also very mean to a 8" princess parrot (the tang was 4" at the time), chasing it non-stop, bashing its tail against it. Well, the tang came out for treatment for black spot ich, and a week later, he wasn't attacking the parrotfish anymore. Now they're best friends, and follow each other around all day like best buds.
He also rarely bothes my blue regal tang (about 4" now).
180G build thread
180G All-glass with dual megaflows in a custom stand
AquaC EV-180 skimmer
250 pounds LR
160 pounds aragonite
Custom acrylic sump from GlassCages.com
2xPCX-40 return pumps
2x250MH 14K, 2x175MH 14K - PFO lighting, 2x65W PC
No-name 36W UV
Water General 125GPH RO/DI