If your bubble rate it to high naturally the mist will be to large. You either need a larger diffuser to handle the increased flow or your BPS needs to be considerably lower, which is ideal in this sittuation. Saturation of co2 is not the name of the mist game, it's co2 direct contact time that your looking for. Mist coming directly in contact with the plant beds is the goal.
So get your flow right in terms of water movement and BPS.
That's what folks need to do with co2 fog...