Respectfully, to the OP...
I can't stress strongly enough, how much you'll grow as an aquarist, by ditching the self proclaimed "tang police" and following the evidence based recommendations of marine experts such as Bob Fenner. There is so much more to successful tang-keeping than tank size. That being said, a properly situated and stocked 75 gallon reef environment with strong current can adequately meet the needs of a number of tang species. The following link is just a glimpse of what's waiting for you to learn...
http://www.wetwebmedia.com/zebrasom.htm
A Fishwatcher's Guide Series, by Bob Fenner, is the proper place for a novice aquarist to seek guidance on perhaps the most important decision in reef-keeping, that being the selection of marine life.