If the shock collar dosent work! let them fight it out they just want to establish the Alpha role and each time u prevent it they will try again!
when i moved i got my first GSD ex police dog and then the next one came and they would fight like mad! i tryed everything! till one day i can home and there was blood was everywhere, inside outside on the walls the ceiling! the dogs where no-where (i thought they had killed each other!). so i searched the flat and pushed the bedroom door open and they were on my bed licking each others wounds. they were best friend since and they share food cuddles and all now!!
Delcey
Ps they will hardly ever kill each other (unless they are hot killers)
you could allways supervise from inside and if it gets to the stage of death then intervene!