I use a Mag 5 fractionating pump (made for skimmers) with the intake they come with. Looks like this:
You could easily bring the line from your CO2 bottle up into the aquarium and stick it into the intake pipe and do the exact same thing. When I did it that way I cut a 1" long piece of wooden chopstick and stuffed it into the end of the CO2 line. That wasn't necessary either but I was trying to make it a little quieter.