More plants and more hiding places. In a 10 gallon you need to have it packed so much with plants and other crap that you can barely see the back of the tank. Also watch out for that filter, I had it on my sorority and it sucked up 2 of the girls and killed them. I would advise a sponge filter.
Also from my experience when you are looking for the females, (if you haven't gotten them already), get most in similar sizes, and then buy one that seems a bit more aggressive and bigger then the others. That way the Alpha will hopefully be obvious.