I spent yesterday out at the Minnesota Zoo. There are four absolutely gigantic marine tanks. One is a giant reef (I can't even guess at the actual size of this tank) that has several bottom-feeding sharks, as well as a bunch of other colorful fish. You can see it from above or through a viewing window that runs along the floor) The second is a slightly smaller (by slightly smaller, I mean the viewing window is around 20' tall, and it's probably 30' wide, and 15' or more far back. That tank has several predators (like sharks and moray eels) as well as a bunch of large fish. There's also a feeding time for this tank that includes a QA session. Then there's the estuary tank, which is only about 4 feet deep, but has a very big footprint. There are only two types of residents of the estuary tank, some sort of relatively peaceful, spotted shark, and some kind of ray. The great thing about this tank is it's a petting tank. Then there's the tide pool tank that's filled with anenomes and sea stars. Again a petting tank.