Liquid CO2 getting into your tank!?
In order for CO2 to stay liquid, it needs to either be at a very low temperature (lower than anything the average person can achieve), or it has to be under a tremendous amount of pressure. As soon as CO2 leaves its CO2 tank, it will convert to its gaseous form. There is _no_ risk of liquid CO2 getting into your tank.
If you're having problems regulating CO2 output from a CO2 tank, you don't have it setup right. You need at least 4 things before a pressurized system will work:
1.) A pressurized CO2 tank
2.) A regulator
3.) A needle valve
4.) Silicon tubing (or CO2 resistant tubing)
The regulator should have its output regulated at around 15-20psi, use the needle valve to do fine tuning of the bubbling rate.
Every plant keeper who uses CO2 injection in their tanks will tell you, a pressurized system is much better than a yeast system. Though the initial cost is quite high, the system will more than pay for itself over time. I spend about 20 bucks Canadian a year on my pressurized system. Every 6-7 months, all I need to do is unhook my CO2 tank, take it to a welding shop, swap it for another tank, and hook it back up to my tank. Pretty much a plug and forget kind of system. Looking at how much I'd have to spend on something like sugar, jello and yeast, plus the time I'd have to spend every 2-3 weeks replacing the yeast system, I'd much prefer a pressurized system.
-Richer