By putting the fish tank on wheels, the fish has the run of the place, and best of all, it actually gets to control where it goes.

The tank sits on a four-wheeled cart which is powered by a small electric motor. A camera connected to an Arduino processor looks down through the water and senses the position of the fish against the white base of the tank. This then connects to a BeagleBoard computer which controls the drive motor and steering. When the fish swims to the front of the tank the motor drives the rig forwards, and if it then retreats to the back of the tank the motor reverses and the cart moves backwards. Likewise, if the fish swims to the left side of the tank the steering turns that way, and vice versa.