They will not reach 15", 10" is a stretch... Here is a thread I started about them. http://www.reefcentral.com/forums/showthread.php?t=2293760.
What other fish are in the tank with the parrot? 5" is considered a small one, usually come in around 7"
I have one in my mixed reef with about 30 other fish. No problems at all with acrylic, corals or aggression. They are hard to find so if you find one and want it, I would get it. They are easy to keep alive and pretty ick resistant like most wrasses.