Alkaline/Acid Buffer

[Jsylivant]

I purchased Seachem Acid Buffer, Alkaline Buffer, and Equilibrium to reconstitute RO water to use in my 50 gallon freshwater community aquarium. My goal was to achieve water with GH=6,KH=6, and ph = 7.0. I added your Equilibrium product to raise GH to 6 dGH. I then added Alkaline & Acid buffer in a 2:1 ratio. I was unsure of the quantity to use, but finally decided on 70 grams of alkaline buffer and 35 grams of Acid buffer. I arrived at this from the label of the Alkaline buffer which said add 7 grams per 10 gallons. I tested the water and found KH=6 and GH=6. This was as expected from the product labels that state how much KH is raised and lowered by the two types of buffer products. I measured ph to be 7.0. An hour later, I retested the water and found that the ph had shifted to 7.8. I was very surprised since I thought I had “buffered” the water at 7.0. My tank has no fish so far and only a few plants and it is aerated. After much forum reading, I learned that in a carbonate buffer system like this, ph is very dependent on the amount of CO2 dissolved in the water. Apparently due to aeration, CO2 is in equilibrium with the atmosphere and is about 2 ppm. From tables relating CO2 to this buffer system, ph will be high, i.e. 7.8. A ph of 7.0 would be reached only by raising CO2 to approximately 25-30 ppm. ppm. I understand that some planted aquarium keepers inject CO2 gas for this purpose. I think the initial reading of a ph of 7.0 was due to the CO2 resulting from the reaction caused by adding your acid buffer product and that when aeration drove off this CO2, there was no source of acid for the buffer system to work with. I intend to keep a non-CO2 injected aquarium with community fish such as swordtails, zebras, dwarf gouramis which books say like a ph of 7. I assume the fish I buy would be acclimated to such a ph and would be stressed by moving them to my “buffered” water with its ph of 7.8. It appears that the ability of a 2:1 mixture of Alkaline and Acid Buffer is only able to maintain a Ph of 7.0 if there is significant acid available. I have read that adding fish to an aquarium does not significantly increase the amount of dissolved CO2 so I wonder where enough acid will come from to move ph back to 7.0? Do I understand correctly that in the absence of fish wastes and plants I should expect the ph of 7.8 and that achieving a ph of 7.0 will have to wait for an acid source from either plants or fish? For start-up, how can I move fish from a ph of 7.0 from the store where I buy them to my ph of 7.8? Do you have recommendations or clarifications to my understanding?