Milwaukee Instruments MA957 Dual-Valve CO2 Adjustable Flow Pressure Regulator with Dual Gauge (psi & kg/cm²) - Perfect for Aquarium, Homebrew Beer, and Industrial Gas Applications

I just started using a CO2 injection setup in my planted aquarium. This one is complete and ready to hook up to a cylinder. the instructions are printed on the box and are very easy to follow. One note, don't make the same mistake I did, make sure the bubble counter has been consistent for at least 24 hours before you put fish in the aquarium, I didn't, I made an adjustment on the main knob then I left for work, When I came home from work, all my fish were floating and the bubble counter was spewing CO2 and had splashed out all the water in the chamber!!! All the fish and shrimp died except my male Betta, he could breath on the surface. Also make sure you have a CO2 indicator in your tank. I use the Red Sea indicator, it's fast and accurate and cheap! Hope this helps.