This is NOT A VERY AGGRESSIVE FISH.
Oscars are cichlids that need attention and good care.
A full grown pair of oscars (12-14") need at the least 100 gallon tank.
Breeding:
To breed oscars you NEED a minimum 100 gallon aquarium, buy 4-6 juviniles to grow out. Then you can ONLY hope for a pair. While growing out the juvinlies i would reccommend atleast 50% waterchanges a week besides massive filteration and massive feeding (these fish eat alot). When your fish have reached about 10" start doing large waterchanges (60%) a week for three weeks in a row, then the 4th week, feed little as nothing, then do 60% waterchanges and feed well next week. Then something should be going on.
I recommend for you to experience keeping large central american/south american cichlids for atleast a year before trying to breed cichlids that are concidered hard to breed (oscars, Electric Blue Jack Dempsey, Cutteri, Amphilophus Alfari and so on). I would start off with a 55 gallon tank with a firemouth pair (Thorychtis Meeki).
Regards from Iceland.