Doesnt seem to me like it's a good idea to buy a fish and not know how big it gets, what it eats, whether or not it is aggressive, etc.
Hopefully, my friend, you have an EXTREMELY large tank.
If you truly have a YellowMargin Trigger, you better start looking for places now, to get rid of it.
They'll max out at almost 24" long and are MEAN. It is VERY common for them to attack divers.