Offgassing Co2

Hi everyone! I am experimenting with using a yeast reactor to add CO2 to an aquarium, using a cycling aquarium with no livestock or plants and in darkness to prohibit algae growth. The reactor - which consists of 500 ml water, .3 ml baking soda, .625 ml corn starch, 1.25 ml yeast, and about 97 ml raw yeast, and heated to 25 celsius for consistent CO2 production - is working FAR too well. Even with an internal filter accomplishing 16 turnovers an hour (currently set to about half that) and outputting the water a centimeter above the water line, the drop checker is bright yellow and the PH is 1.4 orders of magnitude lower than it is when the tank water is offgassed (the difference was larger when I used a 1 liter version of this reactor). I highly doubt that the plants will absorb that much CO2; they certainly will not do so at night. How can I off-gas some of that CO2? I am currently experimenting with an air stone to supplement the filter, but I suspect that this will be too potent (plus I have read they do not promote good circulation in the tank). Thanks