I seem to remember an aquarium being installed in a car on Pimp my Ride a loooonng time ago, but they didn't do anything to account for the movement of the water as the car was being driven. They just kind of positioned it between the back seats or something, the poor fishies. I hope that car owner took the tank out when the cameras stopped rolling.
I know they make cars that are supposed to be low shock and you aren't supposed to feel the bumbs and dips in the road, but even that won't keep you from feeling the car turning, and that alone would throw water everywhere. Some sort of gyro system might help with keeping the fish upright in the tank, but when you turn a little strong there will still be a pull caused by the centripetal force which (I think) would cause the water pressure to fluxuate and might be pretty stressful on a fish if they have to endure it frequently.
On a side note....I think stuff like pistons and/or a gyro system could look really cool on a non-mobile tank! I'm picturing something stem-punk. Oh! and for the inside of the tank, you can have gears as hiding places and wires as the "plants" (of course with no real metal in them).
i've been wanting to make a steampunk tank for a long time....build a wood and brass framework with gears and pseudo-scientific gadgetry around it, and decorate the inside like a victorian curiosity cabinet...with fake medical oddities and suchlike.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger-all down here on Earth.
Loki/Grendel/Gail/Beowulf/Camilla/River/Bathory/Arwen/Lafayette/Deb/Jack Skellington (soon)