Megalodon.
Nahh, just a couple of Fluval 406s, maybe a bottle of bloodworms, and a WC. He'll be set then!
I would divide the tank into 3 different sections.
7,000 gallons would go to a thousand angelfish
1,000 would go to Oscars
And 3,500 to a good heavy community of Rummynoses, black skirts, diamond tetras, galaxy Rasboras, red eye tetras, platys, swordtails, etc.
And 500 to a couple freshwater string rays
thats 12000 gallons
i would get a large acrylic cylinder and fill it with motoro stingrays, oscars, red devils, red tail cats, giant gourami and arowanas