[plantbrain]

a clouple of things will help, fig 3 is good and will help, you should have the CO2 venturi recirculating level set at about 3" down in the reactor tube.

You need some room for the microbubbles to coalesce and get simple diffusion via the layer.

Adding a small diffuser disc might also help, then blast that around the tank without the Reactor there using the XP3 spray bar.

If you want the reactor still, I think you need to disperse the outflow from it better, add another reactor tube on the other side, or place a small poqwerhead near the bottom of the out flow the blast the CO2 rich away into other parts of the tank etc.

These might not be acceptable ideas for your goals.
But the disc idea would solve them also.

I tend to use disc and blast the gas around by placing the spray bar vertically in the corner of the tank and place the disc down low near this outflow.

I direct the mist to be blasted around the back wall of the tank which is the longest straight area and where you generally don't see the mist and where most of the plants are anyway.

This hides things well and gets the most of the gas.

Regards,
Tom Barr