Not meaning to bash your thread but I don't think you will ever sell it for that price.
My liquor store has 20lb tanks full with current hydro for $100. Figure $20 for a fill and $10-20 for a hydro and you should be selling as is for $40-60. I just sold a 1/2 full 20 lb tank on here for $50. I didnt get ANY replies when I listed it for $70.
Like I said, not meaning to bash just trying to help you sell it.