Against other clowns n their owwn they are very aggressive unless they be come a paired. Besides that i am able to keep a paired mocha clown, paired percula, and a yellow bar maroon a lightning clown that have paired up, all in my 110g mix reef. All clowns have been in there for almost 2 to 3 yrs now, except lightning which i added about 3 months ago. All are coexisting so far n not tearing each other up...