I think it depends on how your rock work is set up.
I had 12 in a 180 gallon tank, and while they did like to dart in and out of the rocks frequently, the tended to stay in the area of 1 large rock structure I had to the right side of the tank. Flow was provided by 2 Vortech MP40W's, and about 900 GPH through my returns from the sump.
They would occasionally chase each other the length of the tank, but that wasn't nearly what I would call the norm.
I had 10 females and 2 Males. I wouldn't go more than 5 on a 3' x 3' cube. Start with 3 and see how they get along (start with all females if at all possible).