In the rare cases that I remember reading here where someone 'gassed' their fish with DIY, they didn't have a proper mix that lasted for a couple of weeks.
The safest option is obviously to run an airstone, and I think it's hard for people in good conscience to recommend against it, but I think you are about to find out how hard it is to get good CO2 absorption, and how hard it will be to get small bubbles out of your nano-diffuser.
65 gallon journal:
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