This seems pretty obvious after the fact but I've never seen it mentioned so perhaps this will help someone else I just discovered that my old CO2 inline reactor had a design flaw that was made much worse now that I'm using it on a smaller tank with a lower pressure pump. Here is roughly how it looks Water enters from the top and CO2 from the side. The problem is that the connector coming into the top is quite long and create a fair amount of space where CO2 can get trapped at the top of the reactor and not get churned (well) by the water. This meant that for the first few hours my CO2 was very low and the reactor only really started working well once the CO2 trapped at the top got below the level of the inlet. I've filled the gap with silicone so I'm hoping to see an improvement now. BTW does anyone have any suggestions for how long a rector should be, does it matter as long as its not able to push the bubbles out the bottom?