wait... you're going to make a whole on the hard wood floor, then put a new foundation and a huge cement slap for the tank...? or is your hardwood floor resting on cement and you have no crawlspace under the house....? i'm confused...?
at my buddies, we had to break some of his tile, then made a pretty decent sized slab of self leveling cement for his 180... it had broken and flooded his house before hand... it was a mess...