I would suggest buying a check valve. Place it in between the inline atomizer and the bubble counter. When you turn off the canister for maintenance, water from the atomizer will bleed back towards the bubble counter. A check valve will stop this from happening. I highly recommend the CO2 Art check valve.
Regarding not having bubbles in the tank, the only way this is possible in by using a CO2 reactor. You can see the mist in the attached photo. I would suggest buying a backup diffuser so you can swap them out periodically. I clean mine by placing them in a 50/50 solution of bleach and water. I have used inline reactors since the came out. The newer flow through models allow you to exchange the diffusers (such as the CO2 Art version). I hope this info is helpful.
Respectfully,
Stuart