I'm trying to find the effect of pH on living things like E. coli and such. At first I thought of using a buffer solution which maintains its level of pH, but it's possible that the inactive ions of each buffer have their own effect on living things that I can't account for. On the other hand, I could use hydrochloric acid and sodium hydroxide at different concentrations by diluting it. This will be a little bit more effort (I'll be diluting the acid and base myself), but much cheaper than the buffers, and I'll know that the only other ions present beside H+ and OH- are just Na+ and Cl-, the ingredients of table salt. According to this paper, the effect of pH on the population also depended on the acid (HCl vs lactic acid).
I would like a second opinion on this: If I'm investigating the effect of pH on growth of living things, do I use specially made buffers or just properly diluted HCl and NaOH?