Ok, this can be a long post, maybe it can be a sticky or be part of a beginner FAQ:
Basic things of a CO2 pressurized cylinder unit:
CO2 Cylinder
Regulator (Manual or Electronic Solenoid)
Air Hose
Check Valve
Bubble Counter
Diffusor/Flipper/Reactor/Etc
Things good to have:
Timer (if using electronic solenoid)
CO2 Air Hose (more expensive, meant to combat the corrosion caused by the CO2. Usually black in color)
Accessories to have when setting up unit:
Spanner to tighten the regulator unto the Cylinder
Things to note after purchase:
After purchase, install regulator and DO NOT use it first. Open the main valve (the big one) on the cylinder and leave it overnight and check if the reading on the gauge is still the same to check for leakage of regulator.
If its an established tank, introduce the CO2 slowly, don't have 2bps at one go. Increase slowly daily. Use the
CO2 ppm (pH/KH) relationship to determine CO2 levels and maintain at 30ppm. If you are using ADA soil, don't use the calcuation and use observation to set the bps at the maximum level that the fishes are comfortable with.
-Calvin