I am not sure if your tank has standard dimensions, but here is a link that can give you some idea, since the tank will be very heavy at that size, even when empty.
, I am not sure how accurate these numbers are, but it will at least give you somewhere to start.
Freedom is the sure possession of those alone who have the courage to defend it. -Pericles
Let every nation know, whether it wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship, support any friend, oppose any foe to assure the survival and the success of Liberty -JFK