The 900 lb to 1000 lb estimate was figuring a 5''x 35"x14" tank (17 cu ft without the trough/gathering well) using 64.5 lbs per cu foot (which is the approximate weight of water) would result in a full tank weighing roughly 1088 without the weight of the tank itself. Diesel
fuel is slightly lighter.
17 cubic feet results in a 151 gallon tank.
Jeff