Just hook up the regulator first, and maybe do it outside. I keep my tank next to the fish tank. If your needle reads anything over 1500psi you are definitely overfilled. Typical is 1000psi. But then again I use a 20 lb tank.so if i store the co2 tank under my fish tank and lets say that the safety release blew and all the gas came out in a super cold state and it froze everything within 2 feet. would it freeze my tank bottom and make the glass crack, dumping everything on the floor? im just trying to think of a good location for it.
By the way you can get tanks off craigslist, mine was $60 for the 20 lb. It was from a soda machine.