Christin - check out Rex Grigg's website (rexgrigg.com ?). Google it.
He sells CO2 tubing that is killer. I have proven, to my own satisfaction, that with some reasonably sensitive equipment that under fairly low pressures most silicone tubing leaks gasses. Rex's does not under the same circumstances. I highly recommend it. It will extend the life of your CO2 supplies.
I have a 75g tank, and I use little bitty 5 lb tanks, and they last in excess of 6 months apiece. I firmly believe that one major factor is that my tubing (from Rex) is virtually lossless.