I just bought a used tank. Where can I get the rest of the stuff to complete my system?

Since this is a used tank, the first thing you should check is the test date stamped at the top of the tank. If this date is greater than 5 years old, you will need to get the tank "squeezed". Squeezing is a process to make sure the tank is safe for use and will not rupture when filled with compressed gas.

There are basically two styles of regulators, single gauge and dual gauge. The single gauge model shows the output pressure while the dual gauges show both tank pressure and output pressure. Regulators are available at welding supply stores, hardware stores, and possibly a home brewers supply outlet. There are mail order houses, Grainger or McMaster-Carr, but it would be better to actually see what you need before ordering. Welding supply stores will probably have the best prices. Since this will be the most important part of the system, DO NOT skimp here. Buy the absolute best you can afford.

Needle valves are used to further regulate the flow to achieve a very slow metered delivery. Nupro has a line with the "S" series designation and Parker HR-1 are two popular choices. Whichever valve you use make sure pressure rating exceeds the maximum tank pressure. In the event of a regulator failure, full tank pressure will be delivered to this valve and if underrated ... BANG!!!! If the pressure rating is lower than the maximum tank pressure, install a pressure relief valve that is rated lower than the needle valves maximum pressure rating.

The next component in-line (although not absolutely needed) is a solenoid valve. If you intend for the CO2 to be delivered 24 hours a day, do not invest in this. If you intend to shut the CO2 off at night or regulate the CO2 saturation by means of a pH controller, this is necessary.

To adjust the needle valve setting, a bubble counter is needed. A fine tuning of the needle valve will be needed until the CO2 saturation level reaches 20ppm. Once this is achieved, use the bubble counter to count the CO2 bubble per minute for future reference. Once you have all these settings made, record the output pressure of the regulator and bubbles per minute. This will provide a balanced delivery throughout the "charge" of your compressed cylinder. When the cylinder is changed, recheck all of your settings to ensure they are the same as your previous records.

Research the various methods of CO2 delivery (diffusion bell, reactor chamber, air stone, delivering into filter intake). For tubing choice, there are many different opinions. Silicone tubing is a popular choice while others have had no problem with regular air line tubing.