Adding anything after a yellow tang can be problematic due the territorial nature of the yellow tang, not just fish of the same shape and color. Obviously not all yellow tangs are going to have the same personailty, however, in general that's just how they act. In my case, I added my yellow tang early on and every time I added something fter, the yellow tang would chase it around and harrass the other fish for 3-5 days, then leave them alone. This could be a fatal problem for a fish that is easily stressed out. Just something to keep in mind.