Carbonate hardness or CH value is an important pillar in pond environment. The carbonate hardness is also referred to as temporary hardness. It is also referred to as acid binding capacity.
Carbonate is formed by the binding of free carbon dioxide (CO2) to calcium and or magnesium. In this way it forms a carbon dioxide (CO2) source for water plants and algae. If the environment (micro-organisms) releases a sufficient amount of CO2 to cover the need for plant growth, the CH value will remain stabilize. However, if the need of plants for CO2 should be higher than the supply, the CO2 source from the carbonate will be used, whereas the CH value will decrease. A proper CH value will be ranging between 6° and 10° GH. An simple test will enable you to determine this value too.
If the development of the pond environment should stagnate, the carbonate hardness will decrease, which is accompanied by an increasing pH value. In case the free carbon dioxide should increase on the other hand, the CH value will increase and the pH decrease. This can be observed especially in autumn and in winter, when the growth of water plants is decreasing or stands still. For it is a question of decreased absorption of CO2. This natural process of carbon dioxide binding will prevent acidification of the environment and it will take care that lack of oxygen cannot occur. For that matter carbon dioxide can only bind if the GH value will be high enough, over 8 °GH.
In new ponds and also in stagnating ones, it can be necessary to increase carbonate hardness.
There are special tabs for this.