I need some advice on my new jack Russell staffy pup, Charlie (18weeks old) and my other family dog, Chinese creasted x bichon poodle, Simba (8yrs old). Simba usually lives with my parents but we visit a lot and Simba visits us a lot too. Simba really doesn't like Charlie at all and growls at him a lot. Though toys, food and certain areas make it worse it really can be any time. Usually it is just growling and teeth baring but sometimes it really looks like he will bite Charlie if we re not around and about 2 times Charlie has looked like he might bite back. I'm getting quite worried about it now. Any advice on how to stop this behaviour?