I am at wits-end with this issue and have a smaller and smaller window to accomplish this as the days go by as i will be deployed with my unit here in the next few months. I have the CO2 tank, the hoses, the gauges, the diffuser and the fully functioning planted aquarium but, i do NOT want to nor will i be able to manually turn the CO2 on/off every day so i would like to purchase the device which would make this possible for me. In doing my research i believe that this item is known as a "Solenoid Valve" but, no one i've spoken with can give me a straight answer. I have spoken with gas providers, keg distributors, welders and an assortment of other random applicable resources with no positive out-come.

           I simply want the CO2 to insert via a timer which will be synced with my lighting so that when the lights go off, so does the CO2 and back on again accordingly. What i need to know is the following:

A) Is the "Solenoid Valve" what i am looking for, which would allow me to accomplish said task?

B) Where do i get the damn thing? (Online would be fine but, i need to know the product is reliable and priced within reason)