I have had yellow tangs in a standard 55 gallon on and off for years. The first one did fine with me for 3 years, sold the tank and animals to a friend when I did a multi-state move. Second one has been going strong for over 7 years and is now in a 60 gallon which at 36 inches is shorter by about 12 inches than the 55. He races around, in and out of the rockwork which I purposely set-up with him in mind so he had plenty of spaces he could run through without having to slow down, but he has found many more which he will explore slowly. They aren't as scatter-brained as Dori in Finding Nemo will have you think, their smart enough to know where they are and what they can do. Yes, he has remained small, its only about 6 inches lone but as healthy as could be, thick muscle mass in the area above the eyes, no sunken in stomach, etc. I have to supplement feed, but he constantly picks at the LR. My point is I don't know about a 30 inch tank or trying one in one of those "mini" tanks, but the people who get all in a huff and start the "prison" talk about tangs in a 55 or 60 gallon are just ... Well, I'll stay civil. I care about my fish too, they are also part of my family, and my tang is a happy, healthy, well-fed member of my family. One yellow tang in a 55 or 60 is just fine.