Yes, youngsters will attack each other and, certainly with some species like P ornata, the males recognise each others sex way before you can tell what they are. Mostly I now keep hatchlings individually and they do grow faster that way. I'm not sure if the bigger enclosure is causing the increase in growth rate or if it is just because there is less stress than keeping them all together in a small tank. Female hatchlings of P laticauda will show dominance and cause a slowing of growth to one (or both) if kept 2 to a tank. Interestingly, I've noticed with a few species that if you keep a high concentration of females in a smallish tank, they get on better than if the same number were in a larger tank. It's as if the small tank does not give them an opportunity to establish territorial behaviour (that's not to say that the situation is optimal just because they are not physically attacking each other). I think this is the reason why it can be easier to establish a group of say 1:5 adults than it is to establish one of 1:2....but for good breeding purposes 1:1 is still best in my opinion.
