I think 10 would be plenty. I got my pair from Todd. Beautiful fish, and he shipped them very well. Both in seperate double bagged breather bags. The male poked a hole through both with his dorsal spine, and the female mad it through one. I don't know what he has in stock right now, but he might have a younger pair.
As far as feeding bio-gold, I see no problems. With keeping the temperature low, they do well at low temperatures, but it's not necessary. It just means you don't need a heater. I kept mine at 82, and they bred the week I got them. I don't know where Bill and Todd keep theirs, but 82 worked for me.
And Bill, I'm so sorry that your female died. I really hope you can find another one, and I feel your pain.