I just finished making a Barr Venturi reactor, per the sketch on Tom's website,
Barr Report - Venturi Design
. I used a Catalina 400 powerhead, because it is cheap and about the right size. The tube is a Viewtainer Viewtainer Plastic Storage Container
2" x 6". The elbow at the outlet of the powerhead is from the lawn sprinkler area of the hardware store, an elbow going from 1/2" tube riser to 1/2" male threads, with most of the female part cut off so it fits into the viewtainer. I used a piece of a powerhead outlet deflector to make a prop to better stabilize the weight of the powerhead on top of the viewtainer, which has a soft plastic end cap. The suction cups are a hose retaining suction cup for a cannister filter hose, with the hose clips cut off, and everything is glued together with aquarium silicone sealant. I plan to use a small sponge on the inlet to avoid it plugging up with plant debris and snails. Total cost is around $30, including shipping for the viewtainer.