The powerhead doesn't "take and airline tube". You need to find a way to poke it into the inlet area of the powerhead, so the bubbles get immediately sucked into the rotor and chopped up. I have used the smallest powerhead I could find at the LFS, a "mini jet" as I recall, and I have also used a Maxijet 600. Both worked fine in that job.
If you do a needlewheel type mod to the powerhead rotor it works best. I just used a hot needle to poke holes in the rotor paddles, but there are more sophisticated mods that probably work better. I think all of the powerheads I still have have the holes in the paddles. One type that I don't think will work well is the Koralia type.
I use a mini Hagen elite as a co2 diffuser as described in this article and it works surprisingly well. It wont push water around as much as a powerhead, but it will make a much better co2 diffuser than a powerhead and provide some water movement.