I have a 10g with 4 females. There are lots of hiding spaces and they get along quite well. They are all of different size, so maybe that is part of the formula to success. The most aggressive is the smallest (blue CT), but she usually gets put in her place by the biggest (red CT), seemingly the alpha of the group. They are all nicely together in the picture.
Here is a picture of the tank and I just added a java moss on coconut in the empty space right to the pirate boat. One more cave to hide in.