I’d love to see that! It sounds like a special fish.
I’ve watched videos of goldfish that have been taught to swim through plastic hoops in exchange for food. I wouldn’t have the patience to teach them such behavior, but they’re definitely capable of it.
I think it associates the movement with food, I just started doing this little wave thing with my fingers whenever I went in to feed it and it responds now. Dumb luck I guess, but it wasn’t something I intended to do, it just happened.