The R2 Fish School

Wow
Agility training for fish kit
They show you how to train fish the way they train dolphins and seals

The link has some vids of trained fish
http://www.r2fishschool.com/#!amazing-videos-/cpa4x

I was most impressed

Yes, I think my goldfish would have absolutely loved this, but unfortunately I only discovered it several months after he had died. I can't envisage my tropicals being interested in this - they seem far too interested in doing their own thing. I'd imagine that goldfish, bettas and dwarf puffers might engage most with it. On that note, perhaps, @Littlefish should try it with her dwarf puffers, purely for scientific research purposes, of course.