Niger trigger fish with my Tomini Tang

I have a 75 gallon tank set up for my parents in the living room, I take Great care of it and pay close attention to fish behavior. My LFS that I got my niger At said that if he became aggressive I could bring him back for store credit equal to how much he is worth now. He has not been aggressive towards anything that I've seen, but I do hold him responsible for my small peppermints gone missing, that is not a problem though, 10 dollars ain't much. My worry is that when I leave for Marine Basic training the niger and Tomini Tang will be competing for space. I have 2 black Misbar clowns, a yellow Midas blenny, 3 chromises, and of course the Tang and trigger, right now there is plenty of room being that neither are more than 6", but I don't leave for 5 months and I'll Be gone for 12 weeks, would you think by that time they will be competing for space? No rush on the answer, as I have until April.