I do see a small dip in his body before the tail starts, but again, that could just be because he long finned. do you have any other long finned ones for comparison? And i upload all my vids to youtube, and then post a link..its much easier that way.
Is he acting differently than the others?
the one right beside him is longfin. although you cant see that one very well. i only have 2 that are longfin. no he acts the same. eats, chases females, chases males, etc.