It isn’t only clever Border Collies that can learn to move backwards. Clicker training is very effective with all kinds of animals, even fish.
The link below is to a YouTube video by Helix Fairweather, a KPA faculty member, on shaping her fish Cartman to move backwards.
A light is used as the click with the fish. She has taught Cartman other things too, you might want to watch some of her other videos for great inspiration for training! Cartman Learns to Back Up