Studies have shown that fish intelligence is much greater than formerly thought.
Augmented Fish Reality by new media artist Kenneth Rinaldo, is an interactive installation controlled by Siamese fighting fish.
These fish are capable of establishing visual contact with one another even over considerable distances. When they swim towards one another in this installation, they trigger movement by their aquarium.

4 infrared sensors placed around each bowl and and motorized wheels allow the fish to move forward & back and turn the bowls. By swimming to the edge of the bowl, the fish activate motorized wheels that move the robots in that direction.

Humans interact with the work simply by entering the environment, as Siamese fighting fish move toward humans, presumably because they associate them with food.

I saw the installation in Ars Electronica, people say it does work but the fish were probably having a nap when I sat waiting in vain for some movement.

Related: The Roachbot.