Chloramines and its effects on aquarium fish
Chlorine is commonly used to disinfect public drinking water. When chlorine Cl is added to water H2O, an acid known as hypochlorous acid (HOCl) is formed, it will react with ammonia present in the water to form a very stable compound known as chloramines:
HOCl + NH3 =>NH2Cl + H2O
In some cities in USA and Canada, chloramines are used as an alternative disinfectant to prevent the spread of waterborne diseases and to improve the water quality. While chloramines are not harmful to humans, chloramines have caused great concern among aquarists since chloramines are toxic to both marine and freshwater fishes. Unlike chlorine which can be easily removed, chloramines are more complex in its chemical bonding and chemically very stable.
However, when chloramines break down either naturally or through the use of dechlorination chemicals e.g. antichlorine solution, ammonia is released. This is again a toxic substance harmful to aquarium fishes. While a cycled tank with its nitrosomonas and nitrobacter bacteria colonies are able to convert harmful ammonia into less harmful nitrates, the sudden rise in the concentration of ammonia in the water might prove too much for the bacteria colonies to handle.
The harmful effect of ammonia is amplified when the pH of the water is high. This effect can be kept in check by the use of pH control tools and a bag of zeolite rocks that can remove ammonia from water. The use of zeolite to remove ammonia should used only in times of emergency e.g. ammonia spike since ammonia is a need for cultivation of bacteria for nitrogen cycle.
Coping with chloramines:
1. use aged water to remove chlorine to prevent the formation of chloramines. To prepare aged water, fill up a container with water and ensure sufficient aeration is supplied to the water to create surface disturbances. The exchange of gases caused by the disturbances will allow chlorine to diffuse out, lessening the occurrences of chloramines. It is recommended that aeration is supplied to the water for 24hrs or more for the complete removal of chlorine.
2. good maintenance of biological filter to ensure minimum level of ammonia. This can be achieved by using good quality filter media or keeping flow rate at an optimum level for bacteria to cultivate.
3. use of zeolite rocks to reduce ammonia concentration in water.
4. use of high quality activated carbon filter to remove chloramines.