I have a 13 year old Queensland Heeler and an 8 year old rat terrier mix. With my Queensland getting older and my kids asking more and more for a puppy, I recently brought home a pup from a rescue that I’m told is lab/Queensland mix(jury’s still out). I got him at 10 weeks and he is now 4 months, and he and my terrier are getting into full blown brawls over food lately. The terrier is not at all a snappy little dog or resource guarder type. She and the Queensland would once in a while get into it if the Queensland tried to butt her way into the terriers food bowl, but it was mostly harmless and over quickly. They’ve always ate right next to each other. The short fuse she has with the new pup with the food is something new and it’s becoming dangerous. It was mostly him just being a dumb pup and trying to eat out of everyone’s bowl, but now it almost seems like he intentionally goes to her bowl soon as he’s done with his and he’s ready for a fight. As it’s gotten bad with him, the terrier now gets aggressive with my Queensland around food and it’s far more intense than it’s never been. I’ve been working hard on keeping them calm and patient during feeding time and also separating the terrier now. We’ve been without any fights the past few days, but today I was feeding them a couple treats, the terrier dropped hers, new pup went for it, and it was game on. It’s nearly impossible to break the two of them up as they are relentless once the fight starts. I’ve always been told it’s bad to separate dogs after a fight but if I let them anywhere near each other within 5 minutes of breaking up the fight, they will go right back at it whether there’s food present or not. As my terrier is only about 25lbs and my new pup is about 35lbs at 4 months, you can imagine how worried I am for the terrier as she refuses to back down. My concern is also how uncontrollably aggressive the new pup seems to get at such a young age. Can’t tell if that’s just fear or genuine aggression. They normally coexist just fine and will play and rough house without any problems, but will become worst enemies over food. Not sure what more I can do or if it even can be fixed. Also maybe worth mentioning my new pup is not yet neutered because we wanted to wait until 6 months, but the older dogs are spayed