I'm not sure the question can be answered ... it almost depends on the individual tang, and how she feels in that moment.
I have a kole and a starry blenny in a 65. For many months, the kole would give chase to the blenny as soon as she saw him, and the blenny became both extremely thin and extremely fast. Then, I moved the tank across the room, and re-decorated it.
The blenny is now free to swim where he wants, and eat when he wants.
I also have a midas blenny, but that one's an open-water planktivore, and the tang ignores him.
~Bruce