PH

The symbol pH stands for “potential of hydrogen E It is a measurement of the free hydrogen ions in a system. Neutral pH is assigned a numerical value of 7.0. As there are less and less free hydrogen ions in the water, that numerical value rises; as they accumulate, it drops. Water with a pH higher than 7.0 is called alkaline, and water with a pH lower than7.0is called acid. Aquatic life requires a pH from 5.5 to 9.5. The pH of fish (and human) blood, and coincidentally the ideal pH for Goldfish, is 7.4. The pH can be measured with a simple test kit.
Numerous factors influence pH. As we have seen above, Nitrosomonas bacteria produce hydrogen ion by stripping them away from ammonia to produce nitrite. These hydrogen ions accumulate in the water, resulting in lower pH. Minerals and carbonates tend to remove hydrogen ions from the water, which drives pH upward. Unsealed driftwood and other sources of organic molecules tend to bind up those minerals and carbonates, so that they can’t grab onto hydrogen ions; at the same time, these organic materials generate hydrogen ions as they decay, and these two factors combine to contribute to lower pH. Plants use carbon dioxide during their exposure to light, and this raises the pH. At night, plants give off carbon dioxide, which lowers the pH. Fish and bacteria all use oxygen and produce carbon dioxide twenty four hours a day, which lowers the pH. Combined, these biological processes tend to have the net effect on a fish tank of causing the pH to move downward into the acidic range. Fortunately, there are molecular”checks and balances against this effect.