Puppy is aggressive with other dog
My parents have a golden retriever, which they've had for about 7 years, and a terrier mix, which they've had for about 2 years. The terrier has always ruled the house when it comes to those two dogs because the retriever is so laid back, but I recently moved back in and brought my 5 months old border collie mix with me (we are not sure what she is mixed with). The puppy is always nipping at the other dogs trying to play, and the retreiver will either play with her or just ignore her. The terrier will get irritated and start fighting with her, which was OK when the puppy was smaller because the puppy couldn't hurt her, and the terrier wouldn't hurt the puppy. But now the puppy is bigger (and realizes it!) and will get aggressive with the terrier when she wants to "play". The other day she actually pinned her down by her next show her she was the dominate dog. I don't know what to do to stop this behavior. I worried it is going to get worse and one day the puppy will actually seriously hurt the terrier, who just isn't strong enough to defend herself in a real fight. This morning the puppy had the terrier pinned in the corner! Does anyone have any suggestions to help me get the dogs to get along and stop trying to dominate each other? I was told I have to show that I am the Alpha Dog so that she will respect me and stop trying to show that she is to the other dogs, but I don't even know how to do that.