Add more dats. Don't go with 2 because they will fight, make sure it's 3 and up. This will spread out the aggression. If you decide to add more NGTs, make sure you have a spare tank running incase they will fight. They're the most aggressive dats.
have datnoids in odds that way it prevents fighting. well it would really prevent but it will help out in the long run rather then having 2 in the tank. especialy ngts your gonna see world war III