Most any tang is gonna be very stessed and sickly in that size tank unless you get a tiny one. The problem is the smaller the tang, the more delicate it is and the more feeding, relatively, it will need since it is growing. Tangs are hungry beasties and your water quality will suffer, stressing the little guy and all other inhabitants. Also these guys are prodigious swimmers, they are used to roaming huge areas of ocean.
I've seen an atlantic blue tang in a tank even smaller than yours swimming happily for over two years, but ... tons of flow (40x/hr turnover), rediculous amounts of food, water changes 2x per week, and the fellow has kept tangs for over a decade.
If you can commit to all that then go for it. Even then you will most likely kill several of them before you are successful. These are the reasons you won't see positive responses (sometimes no response at all) here to questions regarding tangs in small tanks. Don't take it personal. I would suggest a bigger setup or a different fish. if the moral issues aren't discouraging enough, think of the expense. Tangs aren't the cheapest fish.
Happy reefing!