definately together. if you want them to pair up ... this is how i do it ... after acclimating them put them together in a speciman container and release them into the tank at the same time AND in the same place. just lower the container into the water (cover the top) to where you want them to go, and turn the container over so they can both get out at the same place. they may not stay together at first, but there is a chance that they will. i would leave them in the container for a 10 minutes or so and then release them.