Agressive miniatus grouper

[Marcus Rogers]

I have a miniatus grouper in my 150 and he has caused no trouble whatsoever. I have recently added an australian harlequin tusk and he seems to only occasionally pick at him, no one else. The harlequin is still eating but his tail is damaged from the nipping. I put a mirror on one side of the tank and it does keep the grouper distracted and has decreased the nipping a lot but he still does it occasionally. Any ideas of what i should do?

 

[Reefing Madness]