Be sure BEFORE you buy it, to make sure it is eating. Also, tangs are highly susceptible of ich but just because you get a tang DONT mean you will get ich. Mine loves to swim into the power head, and they are mischievous too.
Almost forgot....if you get a tang, DO NOT freak out at night if you see it "smashed" between the rocks or see it like this at night:
Its just sleeping. I freaked when I saw mine "smashed" between the rocks, went in to rescue it and thought it was a goner. This is what it looked like....found out its just a rock hard sleeper. If they dont have rocks to hide in between to sleep, they will lay like this.