Why not do this.

Use DIY CO2.
This will save you a great deal of time messing with it.
Next take a small tiny powerhead, and have the out put of the DIY
bubble into the suction side. Use a rigid juice bottle for the DIY
container.
Plug the powerhead into the lighting timer.

When the lights come on and the plants use the CO2, the gas gets
dissolved and adds it to the tank. When the lights are off, no CO2.

But O2 is directly linked to plant production.
If you have high plant growth, you get high O2 production in your
tank.
So if you grow the plant well, you have sky high O2 levels.
These levels should last through the night fine.

Add more circulation and have a slight surface movement. No surface
movement IMO is bad.

Regards,
Tom Barr