Not to belabor the sciency stuff, but a comment here about pH, because I know this is confusing to some with no chemistry background... as Weezard stated, pH is a measure of the amount of free Hydrogen, which in water is H+, it has a positive charge. Water all by itself undergoes rapid breakdown and reassembly, that is, H2O (or HOH) dissociates to H+ and OH-, then quickly re-combines to HOH again. This process is incredibly rapid and continuous. The measure of free H+ at any moment is pH. But because scientists are nerds and can never make anything easy, it is expressed as the negative logarithm of the value. So, more H+ gives a pH as a low number, and less H+ is a higher number:wtf:. The measure of free H+ in pure water is nearly insignificant, but does have a value, as I explained above. Scientists arbitrarily assign this value as 7. As H+ increases, pH value goes down (we say acidic), and as the concentration of H+ goes down, pH goes up (we say basic, or alkaline). When ions are dissolved in water, which is the case with tap or nuted water , etc., the additional charges present influence the pH as they will interact with, absorb or even generate their own H+. Plants have evolved mechanisms that allow efficient uptake of ions and chelates between pH 5.5 and 7. Out of this range things get ugly fast. That's why you pH AFTER you add all the stuff to your water, regardless of it's source.

Curiously, because pH is measured on a logarithmic scale, each pH unit represents a TEN-FOLD increase or decrease in H+ concentration. The lesson from this is that you must not take for granted the differences in pH because they represent a larger scale change than it appears.

End lecture. Commence toking.