You are going to want to let potential buyers know where the tank is located and whether you will ship or they have to pick it up. This will be a critical factor for most buyers, as they will want to know if they will be able to pick it up locally for free or have it shipped across the country for probably about $100.
For example, if the tank is with you in Torrance, CA, a guy in Florida or New York will not likely want to come get it and the cost of transcontinental shipping will eat significantly into the savings afforded by the low price you are asking for the tank.