In my many years of keeping saltwater fish I have learning many things the hard way. At one time I had a Purple Dottyback in my tank and he was an absolute terror, I tore apart my reef to get him out. I would really like to add a purple fish to my tank and am considering an Orchid Dottyback, from what I read this fish is much more peaceful than the Purple. If I am purchasing local, other than trusting the LFS, how do you tell the two fish apart?