tangs in a small tank, IMO should not be and tehre should not be any stories to tell. But with taht said,
At work, I care for a 55 gallon which housed a 5 to 6 inch yellow for almost a yr, UNTIL the power outage over Christmas. # days, sub-zero with no power is havoc. Anyhow, she seemed quite happy except for the fact that she loved to swim ALOT. aND BYT THE TIME SHE MOVED, IT WAS TIME TO TURN AROUND, SHE SPENT HOURS AND HOURS PACING, wher eour koles ian 75 gallon(much smaller tang) spends time palying instead of pacing, back and forth in and out, stoping to smell the calupera and play with the other fishes. The yellow, frantically jsut darted straight lines, back and forth, almost never straying form her B-line path.
Ater seeing that, I would never consider putting a tang in anything under 4 ft in length, and would always try to get the larges possible home for them, besides, Larger tanks are more fun for us too.