I use Kimbrough Fire extinguisher company in Mansfield. While not the cheapest around, their fills are always full ones. They can also sell you a tank and do the CO2 tank inspections every 5 years (required for all compressed gas cylinders).
I have purchased cheap and pricey CO2 equipment online. I get my chemicals from Greenleaf Aquatics and you can find their info here : http://www.plantedtank.net/forums/11...eaf-aquariums/
. They are a sponsor on the Planted Tank forums.
The cheapest Co2 rig I have purchased is the Azoo regulator with cutoff relay switch and I have not had any issues with them so far. Since I'm lazy, I use a Milwaukee controller that sets my pH at the desired level when lights are on. However, controllers aren't cheap and the probes need to be replaced regularly. Others in the club use less expensive options.
Ask any question you need here and PM your email address and I will add you to our Club email list to send you the next DFWAPC club meeting info. Which I believe is in July.