I bought a bunch of aquarium air pumps, tetra whisper 60-100, I believe. They are decent aquarium pumps around $30 at the pet store. First I had 1 pump for 2 buckets, then I went with 1 pump per bucket then went to 2 pumps per bucket. Finally I broke down and bought a serious pump . It is a sunleaves dura pump 1030gph. And it is much better than the aquarium ones. I believe when your dwc growing the more bubbles the better, I try to keep that water boiling with bubbles.
So spend the $50 and get a serious pump, this one will boil around 4-6 5gal buckets.

Also the sunleaves pump is louder and hotter, but not to bad, I can't hear it with the door open I room away. I also put it on a piece of insulation foam to keep the vibration noise down.