I'm not sure what you mean by "automatic CO2"... You mean a regulator with solenoid? Get an aquatek regulator w/ cool touch solenoid and a 5lb CO2 tank (~$120). You can get a timer for it to become "automatic" and you can replace the needle valve and add a bubble counter for about $50 more. I've replaced my needle valve just recently and it honestly rivals the higher end dual stage regulator I have. See the equipment sticky to get some ideas on how to build an autodoser - I honestly don't do it because I enjoy the routine and it reminds me to hand feed my fish and give them a little attention in the morning.