I'd just have a big tank but nothing too HUGE. You don't stay rich by being dumb with your money.... and unlimited is never "unlimited" and if it is then I'd just buy the whole ocean... actually the entire WORLD!

Beachfront property along the GBR. With all that money I (obviously) wouldn't have to work but I would certainly be able to have a modest tank (i dunno... lets say 375 gallons) that had that beautiful seawater pumped directly in and out. I'd capture stuff along the reef that caught my fancy as well.

Imagine... no more water changes... no more dosing... no more shelling out for Australian corals...

Thats the dream.