I haven't kept any myself, but have researched their needs for my website - perhaps most important is a tight fitting canopy as they are reputed to be jumpers (like most dartfishes). On top of this, plenty of hiding places and a deep substrate and house them with other peaceful organisms. A group of 5 sounds fine to me - best introduced at the same time. With regard to sexing them, I can't find much information, although I'd expect males to be bigger and more colourful - best to observe the group in your fish store and seek advice of staff there.