Is a solenoid necessary? Could I just get the same effect by putting the CO2 on a timer with the lights?
Also, if I go with the GLA regulator, what other components would I need? So far I can think of the diffuser and the paintball tank.
The solenoid is what allows you to put the CO2 on a timer, otherwise it will always be on. It is not necessary but I strongly recommend it. Just saying that is how you get the CO2 to work with a timer.