Yes and no. Fish are unpredictable. Eventually, your PBT will turn the tank into its own tank. It will no longer be your tank. Adding another fish to a qt with a PBT is a bad idea, especially another tang. Size matters here. PBTs are very active and need large tanks. They do not stop swimming. So if you will keep him in a small tank odds are that it will be very cranky and destructive. I recently added 5 fish to my 125g, and PBT was not too thrilled for about 3 days. After that, his aggression went away. All the fish were much smaller than him, and he needed to show them that he was the boss. He isn't, the Yellow Tang is more than capable when standing up to him. IMO, PBT should be the last fish added. Also, don't clip your nori like that, or it will break away and dirty up your tank. Fold it a couple of times and then clip it. PBTs graze the entire day, nonstop. I can put a sheet of nori in my tank right now, 1 hour after lights go out, and he will come out and eat it. Or you can get one of those clips with mash on it for it graze more naturally.