Well darnit if we are going to imagine.. I would fill it with freshwater rays to breed... weather and temp prohibiting. I love rays, such amazing creatures.
I change my mind. I'd do the worlds largest school of giraffe catfish. One hundred million giraffe catfish. And then i'd modify a baby bottle with a pacifier and fill it up with pellets and bottle feed each one individually.
I'd want to place an order from this site (I'm not plugging a business seriously--unless you're living in Brazil you'd have no way of actually getting their fish, but geez if we only had something like this stateside): www.riodocepiscicultura.com.br/