Well I have had my maroon clown for somewhere between 6 and 9 months, but there is no saying on how old it is. It's about 2 inches long but I don't know if that is a proof positive way of identifiying the age of the fish.
2" is very young. But it is probably already differentiating as a female if it has been alone that long. Although I have never tried it, apparently the only way to safely pair maroon clowns is with a barrier between them.
I was asking the thread writer's....I think that 9 months in the tank is enough for the maroon to get his dominance and territory, however, isnc eyour tank is (IMO) HUGE, then you could try it I guess...