Water Chemistry: Passing The Acid Test

Just as the quality of air we breathe is vital to our health, the quality of water fish live in makes a difference to their well-being.

Water from different sources will vary in pH and hardness, depending on the quantity and type of minerals dissolved in it. Fish are found in waters of varying chemistry, and their systems are adapted to the waters of their natural habitats. Thus, it is important to ensure that the water for the particular species that you keep is suited to its occupants.

Generally, hard water species are more tolerant of soft water than vice versa, while both groups may react badly to incorrect pH. Aquarium hobbyists should have a basic understanding of water chemistry and how biological processes taking place in the aquarium can affect water quality.

What Is pH?

All water from natural sources contains acids and alkali. If the water contains more acids than alkali, it is acidic. If the water contains more alkali than acids, it is alkaline.

The term pH refers to the degree of acidity or alkalinity in water. Test equipment is available for aquarium hobbyists to check the pH.

If the acids and alkali are equal, the water has a neutral pH. The pH scale ranges from 0 to 14. Neutral water has a pH of 7. Water with a pH below 7 is acidic: the lower the pH, the greater the acidity of the water. Water with pH above 7 is alkaline; the higher the pH, the more alkaline the water is.

Why Is pH Important?

Most tropical fish require water with pH values of between 5.8 and 7.

Sharp fluctuation in pH can harm the fish. A 1 pH-unit change could indicate a tenfold increase or decrease in the degree of acidity. For most fish, the tolerable range of fluctuation is 1.2 pH unit.

If pH values fall below5.5 or rise above 9, the water becomes either too acidic or alkaline, and damages the fishes’ health. Problems are manifested as severe reddening or slimy coating of the skin, and damaged gills. The fish dart about in the tank and rub against pebbles or other objects. If the problem is not rectified, the fish could die.

What Affects pH Levels?

The pH of water is a function of the substances dissolved in it. Alkalinity results from dissolved minerals, and acidity from dissolved carbon dioxide and organic material. Thus, biological processes that take place in the aquarium can cause pH fluctuations.

When carbon dioxide from the air dissolves in water, it forms carbonic acid, casuing the pH to drop to about 5.3. by aerating the water, you can drive off the carbon dioxide and raise the pH.

In a planted aquarium, the reciprocal relationship between carbonate hardness, pH and carbon dioxide should be controlled constantly. In a densely planted aquarium, the process of photosynthesis leads to too little carbon dioxide being dissolved in the water. In such a case, carbon dioxide should be added to correct the fluctuation in pH.

It is important to control the pH during partial water changes or when transferring fish. This is because organic water discharged by fish causes the water to be saturated with nitrogen compounds, and when the aquarium is filled with alkaline tap water, the pH climbs from the acidic to alkaline range, causing harmless ammonium to be converted to toxic ammonia.

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