No need. If you have 1 male and 3 females, then he will get all of the females pregnant. It's better to leave them be, because if you seperate them, the male will will try to breed with that one female and it will stress her out greatly. The more females you have to a male, the better. It helps to spread the lovin'!! My 2 female Platies keep getting pregnant, but I need 1-2 more females so the current ones can have a break.