I just introduced (a few days ago) a 3in Naso Tang into my 125g aquarium. My half black angel (about 3in) is being very aggressive towards it. (Fin nipping and chasing). Could it be that they are very similar in colors and the Angel is just pissed about it? or could it just be a new fish thing. Usually I would avoid a similar color fish to my angels but this naso tang was given to me by a friend with too small of a tank so I gladly accepted it. Both fish are eating fine (both mysis and nori). Any suggestions on how to either stop it or what may be causing it.