Boy am I in over my head. We already had four dogs, two mixes and two pure American Foxhounds. The mixes are a rat terrier (and almost everything else) mix who is about 45 lbs and pure sweetness, and a Shepherd Lab mix. All dogs were rescued as adults and getting up there in years. My husband was sent a photo and video of a dog in an overcrowded rural shelter who was going to be put down at the end of the week for running out of time. He was a favorite with the shelter volunteers. I said I felt too overwhelmed, but he really pushed that he wanted to save this dog and I gave in. Now the dog is here. We got him dna tested and he's 75% Australian Cattle Dog and then a whole bunch of other stuff in the remaining 25%. My immediate issue is that he's being very aggressive with our oldest dog, the Rat terrier mix, and I'm almost at the end of my rope. The older dog, Casper, has seizures, so that could be a factor. Though Skippy the ACD looks concerned and isn't aggressive at all during the seizures. When Skippy first got to our house he latched onto Casper as his best friend immediately and followed him everywhere, constantly wanting to play with him. Then as he became more comfortable he started playing more with the shepherd mix and the male foxhound. The female foxhound has some health issues and he seems to just leave her alone. At some point in all of this Skippy, the ACD, decided I'm the best thing since sliced bread. This isn't necessarily great for me, since he bites legs and the strategy the behaviorist suggested, of just ignoring him, is leaving me with some big bruises. But the behaviorist was actually helpful (it's all remote behavior counseling) so we went from a dog who wasn't just not housebroken but stubbornly resisting housebreaking and incredibly destructive to furniture, rugs, whatever.... Well now he's housebroken and his destructiveness seems somewhat in check. But the behaviorist said I just need to keep Skippy and Casper separate at all times. Not only do I not have space to do that, but I'm so exhausted. I have lupus and I'm barely sleeping with this new dog in the house causing so much trouble, plus Casper having seizures at night. But now Skippy has gone after Casper out of nowhere a couple times and I don't even understand why. This morning they were happily playing and suddenly the play changed to fighting. Casper won't even fight, he just flops over and goes passive and Skippy will keep biting him. I broke up the fight and the next moment Skippy is trying to lick Casper's face like it never happened. The husband thinks they are in a rivalry over me. It seems plausible--they constantly vie with each other for my attention. Plus if I'm in bed or on the couch it's not enough for one to be on each side, Skippy will always try to switch sides so he can push Casper away from me and be the only one next to me. We really can't send him back to the shelter to certain death, but if there are any ideas that don't involve keeping them separate at all times I'd love to try them.