Serpae Tetras...
Well, they are a lovely fish. I prefer the short fin variety myself. They are the nippiest tetras of the family as far as I have ever observed. I've watched Serpae shred the fins on long finned white skirt tetras. But their color is just beautiful.
To tell male and female tetras apart takes a very discriminating eyes. Males will have taller and a bit more showier dorsal fins. Females will be a gravid type of plump just behind their pectoral fins, a very rounded look because that is where her overies are (although a well-fed male may look just like a gravid female).
Will they breed? Not likely. Tetras are South American fish that like warm waters, low pH, and soft mineral content. I have never experienced tetra breeding in regularly kept community tanks. They are not good parents either, so most likely the female will attach her eggs to a leaf somewhere and then turn around and eat them a few minutes later. Tetras may survive and thrive in a variety of conditions, but they will only breed if the conditions are just right for it. If you wish to breed them you'll have to do some research and work on establishing your tank environment to meet breeding parameters.
All in all, serpaes are a good fish.
~~Colesea