We have two Great Danes and and American Bully puppy. My advice to you is to make sure your GD is very well socialized! The two GDs I live with are not mine. They are a roommates. They were not socialized properly. The male is almost as tall as the current record holder of tallest living dog. He wasn't properly socialized and is now a bit aggressive with other dogs because of it. It is my opinion that it is mainly his frustration in wanting to play with them and not knowing how. I think this because it is what I observed from him when we brought my puppy home. He wants so badly to play with my Fenris but is unsure of how to go about doing so.