I have no doubt at all with some testing and tweaking, various venturis could be utilized for aquarium CO2 injection.

That said, tweaking these to work well for the various sizes we might need for our application is another matter. Generally we are using their application(higher flows/aquaculture etc) and adapting it to ours which tends to be much smaller.

The idea is a worthwhile one.
No crap in the tank, in line, no maintenance, highly effective as well as directional.

The economics are also good if a more market focus product was produced specifically for the hobby. Running maybe 20-35$ for sm/med/lg.

That's where the future should likely end up here.

Regards,
Tom Barr