I would have thought at the end of the video, where all those discus were together they would have all fled from the area with the diver right there. Looked like a couple real aggressive type fish were living in the same local too.
I was thinking about what you wrote about continuous inbreeding. Some of these captive bred fish must have repetitive breedings of brother, to sister, Son to mother, daughter to father, real close inbreeding, and it happens not one generation, but many generations. Aquarium breeding is ok, but really weakens the gene pool.
Great video, really enjoyed it.