Okay, I'll keep an eye on their development. I have a 180 litre tank that's heavily planted (40 gallon, the dimensions are similar to a breeder tank) so they should have plenty of room to mark out territories but I keep an eye out incase I need to re-home/return one.
I'm not planning on breeding them, I just love their behaviour and appearance.
I've also noticed something as I was watching them yesterday. The bigger one isn't chasing the smaller one away as much. If the bigger one does turn to chase the smaller one will back away a small distance and that seems to appease the bigger about 60% of the time. If they do chase them is a much smaller distance.