Halfbakery Idea Implementaion: Roaming Fish

[JessR]

C'mmon folks, Now how about some ideas about how this little ball COULD be made to work,
It was on the website as a fun idea that doesn't work without some helpright?.....

Example, how about a metal sphere that sits at the bottom of the ball.
Use a processor and sensor to sense the position of the fish in the ball, and move the metal sphere (by means TBD) to always be under the fish.
The sphere, being much denser than the water/fish will change the center of mass location and cause the ball to roll in that direction.
How, maybe use magetic fields or magic to move the metal sphere.
You're doing work to accelerate/move the ball system around the floor, so you'll need a power source - battery, corn dog or something. Maybe the fish can be trained to turn a little generator wheel.