The only agression I get is my two sens going back an forth, pushing etc, never any damage, but they are close to the same size an male/female so it makes sense. Never seen my del snap at any other fish haha, so luckily I guess just pellets are food for her.
Good luck to you bro. I hope big boy does not mistake mini as a long pellet stick. LoL I have the same size difference in my tank but the lap never bother the little guy.