I have 2 fish that I think are nanacare anomala or a very closely related species. I bought them over a year ago as "unknown cichlids" and had to ID on my own. I believe mine to both be females...
To answer your question, I would not even attempt to keep a pair in anything less than 15 gallons. While small, they seem to enjoy being able to roam the tank, and will ocassionally squable when getting to close to each other. These are obviously not aggressive fish but they clealy prefer some elbow room