I used all that at one time to control my Ph as well. Now I only use Ph up and ph down from the hydro store and it's balanced better and I use way less then I ever have using Natural methods. The amount of nutrients (as long as your nutrients have buffers) you have in your res helps to keep the Ph in check as well. A 10 gal res will hold Ph better then a 5 gal res will; only because the nutrients have a buffer built in.

I have a fish Ph kit from Milwaukee and even hooked up a CO² tank to it and it worked like a charm when I was out of town. Problem is it only controls the ph one way. There is a Ph up & down as well as a feeding machine but they cost about 2k.

Even if you use lemons, vinegar or the Ph up & down the few drops you use will not dilute the nutrients. The PPM changes as the plants use up some nutrients and deposit back others.

Just a little FYI
Zandor Reviewed by Zandor on . using CO2 to control ph I just found out this incredible thing today. Using CO2 to control ph. Mountainman talked about getting a controller to build a ph adjusting machine. Someone posting about using CO2 to control ph. Armed with my new soda club machine ($79 Edition 1) I was ready for the challenge. Today I measured tap water with CO2 and without CO2. The same with R/O water. Seltzer water is plain water injected with CO2. Here are my results. Tap water with CO2 5.4, 5.0, 5.0 5.1 Tap water Rating: 5