It's easy to get a random male and female to pair off. Mine came from the same shipment, but there were more males than females in the tank and I actually got them at different times (waited a week to see how Tyr fared before getting Zroya) and I had no problems getting them to pair up. I've been told that when I get a new female, Tyr should take to her readily enough. They aren't like some cichlid species (angels, for example), who pretty much mate for life.