T.F.
This is not the forum to post it for sale.
Craigslist is the best place to get rid of something like this. If you can't figure out the step by step use of CL, go to a pet store and maybe they can guide you to someplace who buys used (I know you said it is new but it is 2nd hand since it is not being purchased brand new in a pet store) pet equipment.
For safety purposes, I would not allow people in my house to come check out the tank. Put it in your garage so you don't open yourself up to potential danger of a stranger in your house with you.