they can pair up any after about 8 months as a mated pair, but any 2 oscars no mater the sex will appear as "paired up". from my appearance 13 to 18 months before spawning, and if you see eggs they have spawned or if you are lucky will catch them in the act, other wise you will not know. Also a female will lay wither a male is present or not. that means you may have what appears to be a mated pair but are really 2 females. Catching them in the act is best way to know who, is who. but if they do get fertilized and you missed it, you will at least know you have a mated pair.