ph buffer

So I made the decision to change to RO water because it can be used to create the perfect water levels for any fish you'd like. The problem is, it seems that to do so you have to know quite a bit about water chemistry. Hoping that the experts at TFF can help me out by telling me what kind of...

My tap water is medium on the hardness scale, and the pH is naturally around 7.7 or so.   I would like to start a tank for South American fish that need lower pH and soft-medium water. In researching the topic I seem to be getting mixed opinions on whether to adjust the hardness and pH to better...