That ratio is a good start, however many males will breed only one girl so the addition of another male may be necessary. I'm sure your next question would be you have heard that two males will fight. If you add another male at an early stage given you have the space of course then the two boys are more likely to gel, having said that the aggression shown between two male fish is generally nothing compared to the damage done to a female caused by an over excited male, I have a few tanks with multiple males.