Backyard Aquaponics
A place to discuss aquaponics

All good mate, thought I might have missed something of yours. But anywho, Nebbian or rsevs would be more valuable than my post

Maybe talking out of my butt, but a car flow meter would be calibrated to measure a lot of air maybe 15 to 200 L/s (31 to 423 cfm ) not sure how big your air compressor is but the 2HP unit in my garage is rated at 10cfm.

also the air will be pulsing through the inlet which will make it hard to get a accurate reading.

It might be necessary to have a large still air box to stabilize the air flow? maybe you could use an orifice plate with a couple of pressure sensors (or manometer) on the inlet?

if you want an electronic signal to set of an alarm, a pressure sensor on the discharge pipe will tell you the air has stopped or reduced a lot?