What Is pH And What Does It Measure?

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What Is pH?

pH is often the parameter that most aquarists concern themselves with in the beginning. And I’ll say this: you shouldn’t. It matters very little with most fish (as long you’re avoiding extremes.) And pH, in itself, can often be misleading.

As you may know, pH is the measurement of acid in the water. More specifically, it measures the proportions of free hydrogen (H+) to hydroxyl (OH-, the base ion.) This measurement tells us if the water is acidic, meaning a lot more acid than base; neutral, an equal amount of acid to base; or alkaline, a lot of base. Oftentimes, we hear someone refer to alkaline water as “basic”, which can often be misleading to someone who is inexperienced since it sounds more like “normal” than “alkaline”, but it’s due to a large number of base ions. So, with that in mind, GH and KH play a direct role in these results.

Similarly, each element that comprises this parameter are known as a base, neutral, or acidic element. For example, vinegar is an acidic element whereas baking soda would be a base element.

pH actually isn’t comprised of letters, it’s comprised of symbols. The “p” is actually for the operation -log10 and “H” is actually the symbol for hydrogen. So it’s actually shorthand for the equation – log10[H+]. But, rest easy knowing that you don’t have to memorize any of that.

It’ss measured on a scale ranging from 0 – 14 and the scale is logarithmic. “Logarithmic” is an unnecessarily large word to say that 7.0 is 10 times more acidic than a pH of 8.0 and 100 times more acidic than 9.0. So each decimal point on the measurement of pH really does matter quite a bit.

Examples of pH

Everything has a pH, here are a few as a baseline:

0: Battery acid

1: Gastric Acid

2: Vinegar

3: Orange juice

4: Tomato juice and acid rain

5: Black coffee and bananas

6: Milk and urine (not mixed, I hope)

7: Pure water such as R.O. water

8: Eggs

9: Baking soda

10: Milk of manganese 

11: Ammonia

12: Most soaps

13: Bleach

14: Drain cleaner and lye