Halfbakery Idea Implementaion: Roaming Fish

[phrontist]

I don't know if anyone here is familiar with halfbakery, but it's a pretty neat site where people post concepts they wish were a reality. Anyway, this one idea caught my fancy:

Modelled on those transparent balls you can put hamsters in to let them run safely around your home, this is basically the same but built for your fish.

At some point on the sphere is a watertight, screw-on panel which can be removed in order to get the fish inside. To get the fish into the sphere, you simply push it into the fish's normal aquarium, and the fish will be sucked in along with the the water. Then remove ball from aquarium, dry off with towel, and set the ball on the floor.

Now, I'm pretty sure this next bit won't work, but it almost seems to make a strange kind of sense. As the fish moves toward the edge of the ball, the weight distribution in the ball shifts, and the ball itself shifts with it. Thus your little fishy can swim through your house just as effectively as if you'd flooded the whole place knee-deep in water.

As I said, I'm fairly certain that things won't be that simple, given the fish's swim bladder and its bouyancy and probably lots of other things that I don't know anything about either. I did try to come up with another mechanism for making the ball move with the fish, but the best I could come up with was the equally improbable mechanism of having the water filled-ball surrounded by another slightly larger ball which contains a couple of weighted ball bearings. Attach a magnet to the fish (another potential stumbling block, I'll agree), and as the fish influences the ball-bearings, the ball moves.

Still, even if the fish can't get the Bowl moving itself, the whole setup would make an excellent cat toy.

Now, his grasp of the physics involved is, shall we say, a bit off, but the concept is a neat one. So aspiring and formerly aspiring engineers, how would you implement this? I think you'd need some little turbines so the fish is never really able to move out of the center of the tank. I would make the fish tank cubic and have webcams on the top and side and write software to interpolate position. From there you could move the tanks platform around based on fish position. I think you could pull this off with the KOP, some little water turbine things, and a cheap webcam or two. Would the fish dig it?