Will this idea work?

[krichardson]

I just would like know what is the biggest tank he can get?

 

[Yoimbrian]

Ignoring the concerns others have, digging out that much of your foundation (to make it underground in your basement) could seriously compromise your house structurally.

 

[krj-1168]

First off - the original selection of species IS NOT good. Bonnethead - as already stated needs a large tank/pond - of at least 10,000 gallons/37,870 liters(at a bare minimum) to keep one for it's entire life. Also Bonnetheads are a tropical species - which are known to prey on stingrays (most hammerheads do). If you are set on getting a swimming shark (which looks like a "Shark") - I would suggest a Smooth hound or Japanese leopard Shark(Banded Hound Shark). As they are non-ORV species - which means they don't need the space that bonnets require. For Smmoth hounds and the Banded Hound Shark - you could easily keep one in a 2,000-4,000 gallons/7,500-15,000 liter(depending on the species) pond/tank for life. Also they are very compatible with horn/bullhead sharks- as often they live together in nature. Port Jacksons are a sub-tropical to temperate species - so they prefer cooler waters(72F or less). In addition - Port Jackson's are the largest species of horn/bullhead sharks - possible exceeding 5 feet. Which means to keep one for life - you will need a tank of at least 1,580-2,000 gallons/6,000-7,500 liters.