Why an air pump and not a small powerhead?

[atoll]

This question may have been posted before so forgive me if it has been.
Is there some reason (and I guess there will be) why you/we use an air pump to power the water through my HOG2 and not a small powerhead?

[SantaMonica]

Because you need air/water interface turbulence; not more water. If you want to test this, turn off the air, prop the inside-part open somehow, and point a powerhead inside it.

[atoll]

Nope no need to test it I take your word for it. I was just curious and now I have my answer. Thanks.