Most places I’ve seen use Nitrogen tanks for a mixed gas. You can, however, use a CO2 regulator with a nitrogen tank by using an adapter. I had a few extra CO2 regulators and I use one with my straight nitrogen (coffee) set up and the adapter. A full tank of nitrogen is around 2200psi and most CO2 regs max out at 2000psi on the tank side, so the gauge will be pinned at first until the tank drops below 2000psi.