And attached it to the intake to my Eheim cannister filter. I then drilled a hole just small enough for the CO2 line to go through, then added a fine diffuser stone to make the CO2 bubbles smaller. They are pretty much dissolved by the time they get to my impeller
I've read in a few places that the CO2 might start wear out some of the rubber or moving parts from the impeller, and causing it to be noisy or not work as well after a while (a year or more). If you add a diffuser stone so that the bubbles get small and are mostly dissolved by the time they get to the impeller, then it should be fine.
I haven't experienced it first hand, just something I read.