Might have more look in the old world section. You could always use a divider if the tank allows, that way you can moniter the interactions without risk of physical harm to the female (though make sure the divider is securely in place, I've known some fish go through/under/over to get to the other side).
I realize this is a fairly old thread, but I wasn't sure how things worked out for you, and thought I'd add what I found.
According to this article, your fish are harem breeders, the females remain smaller, but they males tend to be fairly easy on them, so aggression shouldn't be a problem. They also tend to be shy when kept in smaller groups so more fish would be a good idea. Multiple males can be kept together so that should help.
Very interesting fish, hope it's worked out well for you.
I have never had any luck with multiple males together, The alpha male will end up killing any other males. A pair will work together, but its best to at least have a trio so the the males won't harass just one female. Have plenty of hiding spaces for them, They are very shy except at feeding times.
i have the male an female seperate at the moment. the male is fully grown and female is still quiet small. i fear if i put them together he may harras her too much.