Big Apple Chelsea Carbonic
113 Lombardy St,
Brooklyn, NY 11222
they have a service where you leave a deposit for a tank,
and they come to your home, deliver a full tank, and every
time you need a refill, they again come to your home and
swap your empty for a full tank. pretty cool concept if you
don't have a car, don't want to look like a terrorist walking
around town with a "bomb", and can afford their service.
they have a lot of aquarium customers who only need one
tank, and a few refills per year.