If you plan on having any control over how the fry turn out, or being able to have a chance at repeating successful batches of fry (quality wise) I would only put in your 1 best female, and your 2 best males. Spawning mops or soft leaved plants like Kelly suggested are a good means of egg collecting. I would advise against using the 120 right off the bat though, as it means having to put exponentially more food in there in order to get proper food density for the fry, meaning its harder to keep water quality up to the standards that you want. A better solution would be to raise the fry in batches in 10 or 30 gallon tanks, and move your best juveniles to the 120 for grow out purposes. Anecdotal evidence suggests that shallower water produces better shape in developing fry, and it is imperative that you feed the developing juveniles a high quality diet rich in live/frozen foods and a high protein content in order to develop good head growth.