Your right...your probably better off to have a larger female ratio....as for brood size...i believe somewhere around the 40 or so range is about right...as for how many will survive, that depends on conditions...but usually a fairly good survival rate...especially if nothing else is in the tank....just dont test mom and dad when there is young...they fear no one when it comes to brood care...not even you!!! Till death is theyre moto