Gents,
Yep, pax version 310.000l / around 260t - this is with an empty centre wing box.
The freighter version - if it ever will appear - may have a centre tank with about 60t capacity, if I remember correctly.
The kg / lbs / USG saga is correct. BTW: We have run through conversion exercises on Airbusses which is no fun (i. e. lbs to kg).
Final comment: The A380 will have neither drip sticks nor Magnetic Level Indicators. On the one hand, this rules out a number of sources for leaks. On the other hand, I am not overly confident with the Parker FQIS (see the numerous problems on the A3456!), and you also lose a simple mechanical way to check fuel quantities for instance in an aircraft recovery.
Regards,
J.V.