I have a 300 cf helium tank that is just too big for me to use. It's out of hydro, but I'm assuming that one can swap it out for CO2, nitrogen, beergas, possibly costing an extra $35 for a new hydro. Here's the CL post:
(135lbs, 55" tall to the bottom of the valve...so no shipping)
PM me with an e-mail if you need a photo.