pH: is a measure of the acid content of a solution, and is defined as "the negative logarithm of the hydrogen ion activity (=concentration)"

Explanation: The measurement of pH is actually a determination of the "activity" , or concentration, of hydrogen ions, H+. A hydrogen ion results when the single electron of a hydrogen atom is removed; since the hydrogen atom consists only of a single electron, e-, and a single proton, the H+ is commonly called a proton:

If the concentration of H+ in a solution is greater than 1 x 10-7 moles/liter the solution is said to be acidic, if less than this, it is basic, or alkaline. The pH (always a lower-case "p" with an upper-case "H") scale is non-linear and ranges from 0 to 14. A change of 1 pH unit represents a ten-fold change (increase or decrease) in the acid content of the solution; a decrease of 0.3 pH units represents an approximate doubling of the H+. As the hydrogen ions increase, the opposite, hydroxide, OH-, ions decrease, and at a pH of 7 they are present in exactly equal concentrations. The product of the concentrations of the H+ and OH- is always constant (1 x 10-14). Pure water exhibits a pH of 7; solutions of strong acids (i.e. hydrochloric acid, HCl) exhibit pH values between 0 and 2 and solutions of strong bases (= alkalies) have pH's between 12 an 14.

pH Values of Natural Waters

The pH of most natural waters is in the range of 4 to 9. The majority of natural waters are slightly alkaline due to the presence of dissolved bicarbonates and/or carbonates.

The terms "acidity" and "alkalinity" are used to describe the the total resistance to pH change of a given water sample. In aquariculture one rarely measures acidity, but the alkalinity is a chemical value that can be very important to understanding what is going on in a system. In reality, alkalinity, is the "acid neutralizing capacity" of the water.

pH Determination:

The measurement of pH is conveniently done with either electronic meters (which must be routinely checked against known pH standards to insure accuracy) or indicators which exhibit characteristic color changes at different pH values. The former is known as an "electrometric determination" and the latter is a "colorimetric determination".

Colorimetric

In aquariculture, the commonly used pH indicators are bromothymol blue (yellow to green to blue as the pH increases) and phenol red (yellow to orange to red with increasing pH). The colorimetric method is the least expensive but it suffers from interferrences due to colored water samples, turbid water samples, salinity, colloidal matter, and substances which can oxidize or reduce the reagents. Colorimetric reagents, or indicators, are subject to degradation and so are the color standards with which they are compared. No single indicator can cover the entire pH range. In waters with very low alkalinity, the indicators themselves may actually alter the pH of the sample. For the purposes of routine aquarium testing, however, colorimetric indicators and kits are suitable.

Electrometric
(Glass Electrode Method)

Determinations of pH with a glass electrode are relatively free of the interferences which effect colorimetric determinations. The exception is in waters with a high sodium content and an elevated pH (usually 10 or above). Temperature compensating pH meters allow the effects of temperature differences to be eliminated.

Store glass electrodes according to the individual manufacturer's recommendations; usually in deionized water. Rinse the electrode tip with deionized water and then gently dry with a soft tissue prior to use. Calibrate (standardize) the glass electrode with buffer solutions with pH approximating that of the sample. This minimizes the non-linear response error of the electrode. Note the temperature of the standard buffer solution. Next rinse the electrode and dry it as before then immerse in a second standard buffer solution that is about 4 pH units different from the first standard. The reading should be within 0.1 unit of the correct pH for this second standard. Either stir the sample gently, or keep the electrtode tip in motion (in the sample) until a stable reading is obtained.

When only occasional pH measurements are made the glass electrode should be standardized before each use. A pH measurement made with an improperly standardized meter and electrode and no better than, and often far worse than, a colorimetric measurement made with the cheapest liquid-reagent test kit. Where more frequent measurements are being made the standardization should be checked (as detailed above) daily. When an electrode's response is more than 0.1 units off (during standardization) it should be replaced. Typically, electrodes are replaced every 9 to 12 months. The popular pocket pH "pens" are disposable meter/electrode combinations and should not be used any longer than a typical pH electrode would be. Without proper care (electrode storage and cleaning and standardization) no pH meter can be relied upon for meaningful information.

Some aquarists desire to have the pH of their systems monitored on an almost minute by minute basis. While the need for this type of monitoring can be debated the fact is that pH electrodes which are not routinely cleaned and standardized and over which the water is not moving will not provide accurate readings. For these reasons it is folly to expect in situ pH electrodes to be reliable as indicators of what is really happening with the pH in the systems in which they are immersed.

Follow these steps; the “squirt & dump method”:

1) Don’t float fish bags! Ever!

2) Add (“squirt”) both NovAqua and AmQuel in the receiving tank.

3) For tropical fishes, be sure the water in the receiving tank is the same temperature as, or warmer than, the water in the bag.

4) For cold water fishes (e.g. goldfish and koi), be sure the water in the receiving tank is the same temperature as, or colder than, the water in the bag.

5) Remove the fishes from the bag and place (“dump”) them into the receiving tank.

6) Discard the water; don’t put it in the tank.

7) Feed the newly arrived fishes as soon as possible after receipt (usually within 15 minutes).

8) Quarantine all newly arrived fishes for an appropriate amount of time before offering them for sale (usually 7 to 10 days minimum).