it took almost 2 weeks for mine to really come out. even now after a month and a half it still hides if i move to fast near the tank.
getting them to eat is the difficult part. it is not that they will not eat anything, it is the fact that they are so shy.

i am lucky that i am able to put the food in my sump (45' away and in the basement) and have it magically show up in the tank. this allowed the trigger to be out and about when the food hit.
they are also planktonivores so they need to fed often in order to keep them healthy. mine has gotten a bit thin since i was on vacation last week, he was only fed 3 times while i was gone. i normally feed once a day. sometimes twice a day on weekends.
G~