Aquarium Water Conditioning

Aquarium Water Conditioning



Most aquarium hobbyists use regular tap water to fill their freshwater fish tanks because any other method, such as bottled water, would be much too expensive. If you plan to use tap water in your fish tank you should be aware that water straight from the tap is not safe for fish. Most tap water is treated with chlorine or chloramine to make it safe for human consumption but these are the same chemicals which make regular tap water unsafe for fish. In order to use tap water in your home aquarium safely, you need to remove the chlorine. Fortunately, there are several easy ways to do this.

What Chlorine Does to Fish


Tap water is typically treated with chlorine or chloramine to kill harmful bacteria and other pathogens in the water. The levels of chlorine in your tap water are not high enough to harm you or other pets that may use it for drinking water, but it could lead to problems in your tank. While chlorine may not directly affect fish, it could damage your biological filter by killing off the beneficial bacteria needed in your tank to maintain the nitrogen cycle. Without these nitrifying bacteria, harmful toxins like ammonia and nitrites will build up in your tank and the water quality will decline. If this situation is not remedied, your fish could become stressed as a result of poor water quality and they could also be affected by ammonia poisoning, a condition that can be fatal in fish. 

How to Remove Chlorine

There are two methods aquarium hobbyists generally use to remove chlorine from tap water. The first involves the use of a commercial dechlorinating solution. These solutions can be found in the aquarium aisle of your local pet store and they are typically inexpensive. To utilize a dechlorinating solution, simply follow the dosage instructions on the bottle and add the appropriate amount of the solution to your bucket of tap water before you add it to the aquarium. Most dechlorinating solutions work quickly enough that you should not have to wait between treating the water and adding it to the tank. This method of dechlorinating tap water is very easy and favoured by most aquarium hobbyists.


The second method of dechlorinating tap water involves letting the water sit for 24 hours. Leaving the tap water in a large, open container for 24 hours gives it time for the chlorine to evaporate out of the water. This method works because chlorine is a volatile chemical that tends to evaporate very quickly. You can even speed up the rate of evaporation by adding an air stone to the bucket. If your tap water has been treated with chloramine, however, this method may not work. Unlike chlorine, chloramine is not volatile and it will not evaporate out of the water on its own. If you plan to use this method to dechlorinate your tap water, have it tested first to see if it contains chloramine in addition to or instead of chlorine. If it does, you will need to use a commercial dechlorinating solution.