Well Endler, this is a bigtime debate among saltwater aquarists between, CAN it be done and SHOULD it be done...
It certainly CAN be done (others have in the past), but even in the CAN category, it is very difficult. The trouble with the biorbs is first the small size; smaller water volumes are harder to control in saltwater aquaria and these tanks are very prone to crashing. Second major difficulty is the actual construction of the tank. The "orb" structure leaves very little surface area with respect to the volume of the tank. As such, gas exchange is poor, pH fluctuates wildly, and fish CAN literally suffocate as a result.
Then there's the SHOULD it be done part of the debate... Such a tank is very small and restrictive for clownfish. One has to remember that clowns can easily grow to 3-4" in length in the wild, and sticking fish with such growth potential in a small tank is often considered toeing the line of responsible keeping of animals.
Having said all that, my own personal opinion is that biorbs have no place in marine aquaria. Also, even if a biorb is used, clownfish are NOT suitable livestock to keep in a biorb, IMO
