I am not clear on what the advantage is of making a venturi reactor like Tom has posted a diagram of, as opposed to simply putting a ceramic diffuser under a spray bar..

Seems even using Tom's design you still need something to blow the bubbles around the tank..

The diffuser is driven by a powerhead and actively moves the mist around.
It's gentle and slowly downward, but more flowm can be added or 2 or nmore can be used etc.

Regards,
Tom Barr