What's a pH?
by Ruby Bayan
I was first introduced to the concept of pH back in high school chemistry when we dipped little blue and pink strips of paper that changed color depending on the acidity or alkalinity of the solution. Of course, all I had to do was remember the acronym B-R-A, meaning "blue to red - acidic" to pass the subject. I didn't foresee that I'd have to deal with the pH phenomenon for the rest of my life. Now that you're hooked on the hobby, you will have to deal with it, too.
Let's start with what exactly pH is and then we'll elaborate on its role in the aquarium and why you need to know how to manage it.
pH is short for "pondus hydrogenii" meaning "potential hydrogen," "power of hydrogen," "weight of hydrogen," and "predominance of hydrogen ions (H+)" as a measure of the acidity or alkalinity of a particular solution.
The pH scale is expressed as the negative logarithm of the hydrogen ion concentration ranging from 0 [high concentration of hydronium ions (H+) = acidic] to 14 [high concentration of hydroxide ions (OH-) = alkaline/basic]. The pH concept was introduced by a Danish chemist, Soren Sorensen, in 1909 (if logarithmic formulas and chemical equations will help you better understand how the pH scale was devised, and how it is applied, the site on Sorensen would be an excellent resource).
Factors That Affect pH
Pure water has a pH value of 7 which is considered neutral (neither acidic nor basic), and generally the ideal condition for freshwater aquaria. However, various factors can cause the water parameters to swing several notches towards acidic or alkaline, which, although almost negligible, could be fatal to the fishes. Here are some examples:
- Water Source -- normally, tap water would be within the neutral pH range but some water sources are naturally "soft" or "hard," or chemically treated such that the pH level diverts from neutral.
- Substrate and Decor -- your choice of substrate and decorative items will influence your tank's pH reading over an extended period of time. At first, a substrate spiked with corals, shells, or limestone deposits will show high pH levels (influenced by the hardness or mineral content of the water), which could later on diminish as the minerals are used up. On the other hand, the presence of peat, or driftwood that leach tannins, can swing the scales towards the acidic side.
- Maturity of the Tank -- the natural tendency for well-established tanks is to dip towards acidic. Fishes eventually adjust to this trend, but not if it falls into ranges that are already toxic to them.
- Plants -- taking an active role in the nitrification process, plants help to maintain a relatively neutral pH by absorbing dissolved salts and waste products.
- Water Circulation and Aeration -- without adequate aeration, carbon dioxide can remain trapped in the water and lower the pH (make the environment acidic).
- Overstocking, Overfeeding, Excess Medication, Poor Filtration -- in short, inefficient tank maintenance can wreak havoc on your pH levels.
pH and You
Every well-meaning aquarist needs to have a pH test kit handy. Various types of kits are commercially available -- they're mostly inexpensive but will be a valuable tool in your efforts to maintain the ideal home for your pets.
Test your tap water to make sure it's safe for the types of fishes you've chosen to keep. Remember to pre-check the parameters of the new water you bring in when you make water changes.
Test your aquarium water regularly (daily when setting up a new tank; once or twice a week for established tanks).
Consult your local fish store for the availability of buffer solutions in case you need to make drastic adjustments in your pH levels.
See also: Aquarium Hazards