Well, I figure I'd aim for a pair in the 225, provided they're small bimacs - and I have a few spare tanks, including my 300 gallon QT tank, that would suffice, if two tanks are necessary.
If my supplier is indeed bringing in a small cyanea, then it will be alone in the tank, with some edible tankmates. I really enjoy my inverts - even in the shark tank, my urchins and starfish are quite interesting - in fact, people always mistake my huge serpent star for an octopus, when he sticks a few arms out and snags a silverside.