I bred oscars awhile back. I had different pairs. The number of frys depends on the genetics of the female oscars. Some have only a few hundreds and others can have a thousand. The size of the female do not make too much difference. The age they start to show any activity is about one year old or about 6 inches. I had 2 females laying eggs together before also. Some of the imported males are sterile and are not fertile. Tank raise oscars usually don't have that problem. I think it maybe the hormone that is used on them to color them up that causes the the infertility. The females don't usually have any problem laying. The temperature I used was about 82 degrees with lots of live or frozen food. Frequent water changes will stimulate the breeding. Good Luck.