No they don't. Since you have one ocellaris in there, if it's been there for over a month, odds are you have a female. Adding another now (get a small juvi) and it'll turn out male in all likelyhood. They're hermaphroditic. Besides, ocellaris are kinda timid and gentle for a clown. I've owned several and have yet to witness anything even close to aggressive behavoir. Given a sufficiently large enough tank, ocellaris can even be housed in groups, although they will devlope a pecking order and this should be watched to make sure all specimens are getting food.