Joist sistering for large aquarium

[subnet88]

Hi,

I need to sister the joists in my basement to hold my new 330G aquarium.. The problem is, the joists I need to sister are directly above my heating ductwork, and incoming(City) water pipe. A contractor is quoting 4K to take the ductwork down and put it back.

Does anybody know of any alternatives, or could explain the best way to take the ductwork down myself?