Most aquarists use tap water for their aquariums, both for the initial fill up and to top off the tank to replace water lost due to evaporation. If your tap water comes from a private water system that uses a private well for its source, in all probability the water will come from a well which will not be treated with chlorine or chloramine before being distributed to the end-users. This water does not need to be treated before using it in an aquarium.
Municipalities, on the other hand, are required to treat their water with chlorine and/or chloramine whether it comes from a well, a river or any other source. Treating the water with chlorine and/or chloramine is a great idea, since this has the potential to destroy a wide variety bacteria and other nasties that we really don't want to be ingesting if we want to stay healthy, nor do we want any stray bacteria finding its way into our tanks.
The Difference Between Chlorine and Chloramine
Chlorine has been added to drinking water supplies for years to kill bacteria. It has only been fairly recently that chloramine (chlorine and ammonia chemically bonded) has been used in place of chlorine due to its tendency to remain stable and not break down over a short period of time, thus providing protection over a longer period of time.
As many people know, the chlorine will evaporate (fizz off) from water left open to the atmosphere in a fairly short period of time. Chlorine can be removed from tap water by either leaving the water open to the air for a period of time or by introducing air bubbles (via an air pump and air stone) which will accelerate the dechlorinating process.
Chloramine, on the other hand, will remain in tap water for an extended period of time and requires a chemical or carbon treatment of the water to effectively remove it. In order to remove the chlorine, the chloramine must be deconstructed into its basic parts, chlorine and ammonia, with each part being treated to remove them.
Most tap water conditioners will break the chemical bond between the chlorine and ammonia and then destroy the chlorine, leaving the ammonia in the water. The better quality water conditioners will also neutralize the ammonia, which is toxic to fish and invertebrates.
Three Methods to Remove Chloramines From Tap Water
Read product labels closely, and if a product states that it removes chlorine and chloramines, but has no mention of ammonia, beware. Products such as these are designed to break the chloramine bond, separating the ammonia from the chlorine, at which point the chlorine is eliminated, but the released associated toxic ammonia remains in the water. Again, read labels carefully. In all likelihood, a product like this will also state that an additional brand name ammonia eliminating or detoxifying product should be used at the same time.
- The easiest and least expensive way is to use a chemical dechlorinating product but choose one carefully, because not all tap water conditioners or de-chlorinators are the same. The simplest solution to this problem is to buy three-in-one chlorine, chloramines, and ammonia treatment tap water conditioner.
- Install and filter the tap water through an RO (Reverse Osmosis) unit, but make sure it is a quality model that is designed to remove chlorine, chloramines, and ammonia.
- A simple faucet or under the counter tap water drinking carbon type filter can be used, but the unit must contain high-quality carbon, and unless the water is allowed sufficient contact time, it may not be completely effective. Also, chloramines can exhaust carbon much faster than chlorine alone, and therefore filter cartridges need to be replaced more often. Buying a tap water filter that has an indicator that tells you when it's time to change the cartridge is a good investment here.
Disinfection With Chloramine. Centers for Disease Control and Prevention