A local fire supply company is selling used certified 5lb. CO2 tanks for $50 filled. Is this a deal??
My new tank was $80 plus another $10 to fill, so I would go for it. Even if they are used, as long as the cert. date is good, then there's no problem.
I just picked up a 10lb tank from a fire shop for $62 with tax, re-hydro'd and full.
I would suggest a larger than 5lb tank. but 5 works fine.