Re: Reconditioning RO/DI water for freshwater
Good morning, csrbmr.
I apologize for the delay in response, as we were not available over the weekend. I do think that, for your situation, Replenish is the best product for the remineralization of your RO/DI water. Replenish was designed to reconstitute minerals stripped from water during the reverse osmosis/ deionization process. These minerals are essential in osmoregulation of freshwater fish. While Equilibrium will also replace minerals/ restore general hardness, Replenish was designed with freshwater fish in mind, while Equilibrium more specifically targets the needs of aquatic plants.
As far as buffering is concerned, there are two different systems that work in freshwater. The first is a carbonate/bicarbonate system, and the other is a phosphate-based buffering system. Of the two, phosphates provide more overall pH stability. Because your tank is not planted, then I would suggest going with either Neutral Regulator alone or a combination of Neutral Regulator and Acid Regulator. These are phosphate-based buffers, while Acid Buffer and Alkaline Buffer are carbonate-based, so I think your pH would be more stable utilizing these.
So, if you would be happy with a pH of 7.0, then you can go with Neutral Regulator alone. Because your tank is at 7.4 right now, then you may need to add the suggested amount of Neutral Regulator daily until the pH stabilizes at 7.0, at which point you can just add the buffer on an as-needed basis.
If, however, you want to target a pH of 6.5, like you mentioned in your first post, then you can combine Acid Regulator with Neutral Regulator. Using 1 dose of Neutral Regulator and 2 doses of Acid Regulator will set your pH closer to about 6.4.
We hope this information helps, and please let us know if you have additional questions. Have a nice day.