well, considering that 30L of water alone would weigh 66 lbs... and then consider the added weight of the glass, lights, decor, etc... you're looking at suspending a minimum of 70 lbs from your ceiling. probably not a good choice.
consider also the fact that you'd probably also want to hang it from a single point like a lamp--which would render it almost impossible to get a water change done.
I was more thinking along the lines of a baby biorb hanging from steel cable(s) from a pulley attached to the ceiling. This would look really cool but I doubt my parents would let me do it.
there's still the question of how to secure it properly without sacrificing the aesthetic advantages of the spherical shape. a suspension system would have to either (a) connect directly to the top somehow which would obscure water access or (B) sling underneath the bottom which would obscure the view from the sides.
installing a biorb to a heavily reinforced metal wall shelf would probably achieve much of the same "weightless"/futuristic appearance without the safety concerns of a suspended system. but the best, most secure display would probably be to use a pedestal. (perhaps a steel-and-glass one?)