That would be a huge nightmare I had dreams like that before...it also involved being eaten by an anemone, I have a 2 gal fresh water tank break on my dresser after we got new carpet.( mom not happy) but I would be terrified with something 250x that plus being saltwater, what I would reccomend doing is filling the tank up with tap water and letting it run for 2 day so you know the builder didn't screw up.
Jimmy
Post pics as it comes along