uses a large Composite plastic cattle feed container (I think it's a rubbermaid) that came from a Farm Fleet store. It's about 5 feet across by 24 inches deep.
There's an inch or so of sand on the bottom and the whole thing is heated by one large ebo jager and filtered by a magnum 350.
In it they have a shark, carpet anemone, big clarkii clown, stingray, urchins, 2 lionfish, etc.
Thay have had some form or another of open topped tank ever since I have known them and every inhabitant does great. They feed the inhabitants mostly live fish.
If you started one, you would be wise to get some tankwater and live sand from your friendly LFS
to speed up the cycling process.
Hope that helps alittle. It is so fun to pet the stingray when he comes out of the water and flaps at you.
(edited to correct tank dimensions