Aren't you afraid of your tang to get ich? I have a 35 Gallon tank, with 2 clownfish, 1 blue damsel, and 1 Coral Banded shrimp, got around 3 soft corals in there , i do water changes once a week and got pump and protein skimmer.
Honestly, my LFS has a beautifull tang, small tought, its a dark yellow but has big white circles around hes spine, wich i would love to have in my tank.
Im curious, how long have you had the sailfin tang? didn't you have any problems with him?