Not to get too geeky, but you can't change the pH without chemicals - peat releases organic acids (chemicals), CO2 is a chemical, baking soda and phosphate based products (pH down) are chemicals. As a chemist, I just had to respond. I think you may have meant "natural" products vs. "manmade" products, but in this case I think even that is a stretch. Rex is right on - you need to know the chemistry when you start - kH, gH, pH, etc. before you start changing it.
72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias
2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.