one of the difficult things about shooting fish portraits is controlling the background. In this shot, the subject is in the lower center, where he blends into the reef strata. See him now?
I was lucky on //ambergriscaye.com/forum/ubbthreads.php/galleries/251964.html because there's enough contrast between the subject and the background. The yellow and neon blue stands out just enough from the inky blue background to make the Queen Angel easy to see.