3500 Gallon Black Specialty Liquid Hauling Tanks Flat Bottom tanks are designed to be the most rugged and durable utility transport tanks on the market. Unlike other tanks, Flat Bottom tanks provide all the strength you need for transporting liquids without the use of bands. Tanks should be mounted on flat surfaces with full length and width support. *Can be used for liquid fertilizer. See our website about our other size and application water and fertilizer tanks! Our Norwesco tanks are made out of rotationally molded linear, high-density polyethylene resin that provides outstanding environmental stress crack resistance. The resin is UV stabilized.