Here is what I recently posted on another thread that I think will work much better for you.
I suggest looking into a diffussion bell. Tetra use to make them. Then you get 100% gas diffusion. You could easily make one as well using a 20oz soda bottle:
1. cut off the neck
2. Poke a hole in the bottom
3. Insert a piece of rigid line through the hole about 1/2-2/3 into the open bottle leaving about 1/2" out the bottom.
4. Silicone the tube in place
5. Attach two suction cups to exterior of bottle.
6. Attach air line tubing to the rigid tubing coming out the bottom.
7. Invert bottle and place in tank suctioning to glass (let all Air out of bottle)
8. Periodically fill the chamber from your CO2
source. You could even leave it hooked up with a on/off valve just make sure you also have a one way check valve in place to avoid draining your tank.
It provides much better gas exchange than the bubble method.
Not sure what you are using for a CO2
source, but here is a cheap DIY
method that worked for years for me.