If oyu have ever seen the tv show Myth Busters you wouldn;t believe the 3 second memory idea. I would actually bet it can be done and that the video actually has the possibility of being very real. The Myth Busters taught goldfish to go through holes in plexiglass in a tank to get to the food at the end of the tank with the gholes in different areas of each of the 3 sheets of plexi. It took them a whole day to train them so given a couple weeks of steady work I would bet you could teach them to jump through a hoop on command.
Imagine what could be done with a fish that doesn't have the stigma of having a short memory
Although I am not sure that the first set and the second set are the same 4 fish in each.