Are you working on obedience and the program, nothing in life is free? I would up your position of leader and let both dogs know that neither one of them gets to make the rules or decide anything between themselves. They are not in a position to do this if you are a very clear family head. (alpha) If one wants to compare this to a wolf pack, an alpha will step inbetween squabbling middle ranking wolves to prevent or break up a fight. They will not allow it. They do not do anything more than that. I would suggest preventing any argument...don't even let it get started, by physically moving them away from eachother at the first signs and giving a firm verbal command, such as "leave it." (which they should be taught anyhow for many useful applications) Then reward lavishly for their compliance. I would tend to keep them seperated in particularily high stress situations, such as feeding time, when high value toys are in the area, when you're cuddling one.
Not all dogs like all dogs and when it is this extreme, I don't think you're going to be able to change that fact. It's been 4 months and usually by this time, a new comer would have been accepted into the group if it were to be accepted at all. I'm pretty sure about that....could be wrong. I'm guessing you'll have to keep them seperated rather than expect them to get along safely. It's one of those things. I hope I'm wrong about this.
I also agree about the shock collar. It will stop the behavior quite possibly for the most part, at least when the collar is on, but it will also associate the other dog with even more of a rotten situation (shock) and make the one "hate" the other even more. Then down the road sometime, it could happen that the dog does not control it's behavior and snaps. I don't think it's reliable because you're still not dealing with whatever the underlying issue is that the dog has with the other dog. It's still there boiling under the surface.
Not all dogs like all dogs and when it is this extreme, I don't think you're going to be able to change that fact. It's been 4 months and usually by this time, a new comer would have been accepted into the group if it were to be accepted at all. I'm pretty sure about that....could be wrong. I'm guessing you'll have to keep them seperated rather than expect them to get along safely. It's one of those things. I hope I'm wrong about this.
I also agree about the shock collar. It will stop the behavior quite possibly for the most part, at least when the collar is on, but it will also associate the other dog with even more of a rotten situation (shock) and make the one "hate" the other even more. Then down the road sometime, it could happen that the dog does not control it's behavior and snaps. I don't think it's reliable because you're still not dealing with whatever the underlying issue is that the dog has with the other dog. It's still there boiling under the surface.