I have 2 purples and one yellow tang. All three have grown in size in the last few months. The larger purple was probably 3" in diameter, and its now closer to 4", and second purple was probably 2.5" and is closer to 4". The two purple tangs are nearly the same size. The yellow tang has been growing, but at probably half the speed as the purples, he hasn't grown much in the 8 months I had him, maybe 0.05" from nose to tail. He is the smallest of my zebrasomas and is probably 2.5" in diameter.

I have a vlamingi...its definitely been growing, started a about 1.25" nose to tail in March/April, and is closer to 3" now. I can actually see this fish growing from week to week right now. I actually find this fish mimics that largest fish in the tank; at first is was my male trigger, and now its the Naso. Growth spurts seem to come on pretty quickly after this fish has found its new shadow. The personality also seems to mimic the temperment of the larger fish.

I also have Naso tang not growing in length, just width and very slowly at that. The fish was purchased at about 6" in length.