Are you referring to the lieutenant tang by chance? If so they need a 180 gallon tank, they get to be 10" and need room to turn around and swim. They are on the more aggressive side, but not as aggressive as purples, PBTs, sohals, or clown tangs. They aren't as peaceful as convict, hepatus, mimic, kole, or tomini tangs. I think they are more around the yellow tang aggressiveness wise, probably a little less. My lfs told me that they have that name for a reason though.