I have a foxface in both my 180 sps tank and 125 softy tank. In the 180 I also keep a purple tang, yellow tang and a naso tang. In the 125 I have 2 yellow tangs and a sailfin tang. Nobody messes with the fox faces. They all get along, the dominate tang in each tank will flash the others on occasion just to let them all know it’s still the boss but none of them bother with the fox faces in any way. It seems like they instinctively know that the dorsal is venomous.
I put the fox face in each tank first.
In the 180 I added the purple and naso at the same time. I added the yellow later. I got a yellow that was much smaller than the purple, acclimated him for months, made sure he was nice and fat then put him in the 180. He got chased for a little bit but he was still much smaller so not as much of a threat. After a week he was following the other tangs around the tank like a puppy. During the first day or two if any of the tangs got to close to the fox face he would flash and the tangs would hit the brakes.
In the 125 I put the sailfin in first, he was pretty good size. A few months later I added three small yellow tangs at the same time. If they are juveniles they will not show the same level of aggression. They did establish who was boss but having the considerably larger sailfin in with them kept them pretty docile. One of the yellow tangs never looked right, body shape was a little off, if he had ears one of them would have been folded over. I wasn’t going to put him in the 125 because he was deformed then I figured I have one eye and haven’t been euthanized yet so give him a chance. He ended up dieing after about 6 months. I hope I last a little longer.