To determine the environmental conditions of an aquarium, we need a reliable pH measurement. This should also be performed regularly, for example once a week. It is appropriate to carry out the measurement always at the same time of day, to be able to really see the normal pH variations that take place during the day. You should keep in mind that if you want to carry out an exact measurement of the pH, you must use the water sample immediately. During transport, for example to take it to an aquariology shop, the pH value might be altered.
Testing with drops
For the beginner marine aquarist, a common test using readily available drops is sufficient as it is quite accurate. To do the test, a few drops of the solution are introduced in a few milliliters of aquarium water, and then the resulting colour is compared with a colour chart. Your shop keeper can recommend an appropriate test, and the instructions for use are available on the box or in a leaflet contained in it. Before buying, however, check the colour chart, to make sure it matches your expectations. For measuring in sea water you will need a precise result in the range between 7.5 and 8.7. Be careful also to check that the test is not too old (expiry date), and of course that it is suitable for use with sea water.
Those who want more precise information, with decimal numbers, can use an electronic meter. However, this device must be calibrated very precisely for it to provide exact measurements. A pH meter device is certainly better than drops, but in case of erroneous calibration it can become even dangerous, because by indicating the wrong value it can mislead the aquarist. The same, however, can be also said of a measuring solution that is too old, which most probably does not work correctly anymore. Therefore, do not blindly trust the measurement if you get abnormal results but everything in your aquarium seems to be in order.