This could be a big leap sam but it could even be a morrii does the fish have any dark bloches on it, he did say he was the dominant male so he could be a bolder blue because of this.
Sam, I did think that the one hiding in your pic probably was a Cobalt Blue, but without a full shot we will not know. The Morrii has a very pronouced forehead.
Replies to SamUK's post can perhaps be given there?
I must have taken about 85 shots, and it was sheer luck that I got that one . I am using an Olympus SP500-UZ. Still getting to grips with it at the moment.