Acidity / Alkalinity / pH and Tropical Fish
Water is made up from one oxygen molecule and two hydrogen molecules (H20). The hydrogen in water comes in two forms; positively charged hydrogen ions (H+) and negatively charged hydroxyl ions (OH-) It is the ratio of these two ions in the water that determines the acidity or alkalinity, which is measured on the pH scale.
More hydrogen ions results in a more acidic water (lower pH) and more hydroxyl ions results in a more alkaline water (higher pH) An equal ratio of ions produces a 'neutral' pH of 7.
Most fish live in water between pH 5.5-8.5 The acidity, alkalinity, or pH of water is a different measure to hardness, which is the level of salts and minerals in water, although the two are sometimes related.
The vital functions carried out by a fish's body are adapted to the natural environment they originate from. This means that some fish, which come from areas of acidic water, will only live happily in acidic water, these fish are called acidophiles; fish that prefer alkaline conditions are called alkalophiles.