I think I email this link's owner about the needle valve from Clippard being 10.10$(shipping is 6-8$ or something though) being a much better contyrol device than the cheapy brass fitting valves. But that's my onl;y reservation about the entire system.
It rocks for the $.
Add a 7$ extra nice needle valve and you are set.
FIY:
DIY and Gas systems do NOT need a solenoid to be throttled on/off etc although both can be hooked to do this on either type of CO2 source.
A better way is to use the reactor pump itself.
When it's turned off, then the gas bubbled up and out to the air above. When the pump is on, the suction pulls the bubbles in and atomizes the gas into solution.
Since only positive suction is applied, there's not need for a check vlave which also can fail. If the power head fail, no big deal, no CO2 is being added. If a solenoid fails, more CO2 will be added than you want.
Powerheads run 8-20$, solenoids run 40-80$. Both use about the same electric, CO2 gas is cheap and it'd take many years to make the $ back on gas savings to pay for the solenoid and that's if the solenoid last that long.
Same could be said for the powerhead I suppose but I've gotten a few years out every one I have.
Regards,
Tom Barr