Chorine and Chloramines - the dangers of city water

Read so far

Chorine and Chloramines - the dangers of city water

January 03, 2017 - 09:58

This is an excellent article, originally from an aquarium magazine, that explains the problems of chlorine and chloramines in city water supplies.  It mentions  the chemicals or methods you should be using to treat your incoming water, and I have also made a few Koi pond comments.   If you use city water for your pond, you need to read this article!

Most people take water which comes through their faucets directly from their local water companies and put it into their aquariums. After all, what the heck, why not? It is plentiful and inexpensive. Unfortunately for the hobbyist, every local water company adds chemicals to the water to make it safe to drink. This is a mandated requirement from the United States Environmental Protection Agency (EPA). The two major chemicals they add to the water to kill the harmful bacteria and other organics are chlorine and/or chloramine. Of the many chemicals that may be added to your water by the local water company, chlorine and chloramine, both of which are very different in character and nature, are the two most harmful to your fish. We will discuss these two chemicals in greater detail shortly.

Additionally, many water companies today are pumping water to you through pipes which they laid in the ground many, many moons ago, and many of them are made of lead. Over the course of time, water can have a detrimental effect on lead pipes especially if it is on the acidic side, or in other words, it has a low Ph value. To combat this effect on their lead pipes, the water companies will add additional chemicals to the water to make the water more alkaline or have a much higher pH value.

Alkaline water has a much lesser detrimental effect on the lead pipes than that of the acidic water. And to further complicate matters, this is only the beginning. It would be one story if the water company could guarantee us the same water conditions 100% of the time, but they cannot!
From day to day the chemical structure of our water is very volatile. The water companies do not do this on purpose, but rather it occurs for reasons which Mother Nature herself controls. In warmer climate areas, more especially during the summer months, the bacteria booms and their levels are much higher. For this reason, the water companies will use more chlorine in the water in an effort to combat the excessive bacteria. Heavy rainfalls will also turn the water more acidic, lowering the pH value. Acid rain seems to be the norm in today's world. On occasion, a water company might have their supply of water depleted to the point that they have to purchase a supply from a neighboring water company. If the chemical structure of the water from the two companies is not identical, other variances will be present when it comes out of your faucet.


As I stated above, chlorine is an EPA mandated chemical in our drinking water and must be present at a specific minimal level. More importantly the level of bacteria is monitored and controlled. In order to get the bacteria down to the meet the minimal EPA requirements, the water company might have to greatly increase the amount of chlorine they add to the water. Chlorine has a natural tendency to evaporate from the water over a period of 18 to 24 hours. Therefore, even though a heavy dosage might have been added at the water company and depending upon how far away you live from the water company and how long it took to travel to you, the chlorine's presence will be diminished by the time it comes out of your faucet. However, it is still present in the water and must be attended to before being introduced to your fish.

Why you ask?

As I stated earlier, chlorine is very harmful to your fish even in very small quantities. Very small quantities will cause the fish a great deal of stress while higher quantities are extremely toxic and will kill them in a very short time frame. The good news is that most fish stores generally carry several different brands of products which will neutralize the chlorine effects. The major common ingredient in all of these products is the chemical sodium thiosulfate, which chemically diffuses and neutralizes the chlorine effects instantly. The cost of these products is relatively low, especially if you compare it to the cost of having to replace your fish. If your water contains chlorine, this is an item which I would recommend you have on hand, and more importantly use, every time you make a water change. There is an alternative to using these products, so let me give you the flip side.

As previously mentioned, chlorine has a natural tendency to evaporate from the water over a period of 18 to 24 hours. Therefore, you could put tap water into large buckets or pails and let it sit for 24 hours or so before adding to your aquarium water. It is important that the water have continuous movement during this time to aid in the evaporation of the chlorine. Therefore, I would recommend air being pumped through an airstone be added to each bucket. If you have a relatively small amount of water to 'allow to sit', this may work well for you. If you have a great amount of water to change, buckets and/or storage space might very well be a problem for you, in which case, I would suggest you look into the aforementioned products.

Chlorine has two strikes against it, however, and is being done away with by many of the water companies. Because chlorine evaporates so rapidly plus the fact that it has been proven that chlorine, in conjunction with some types of bacteria which may or may not be present in the water, will form a type of cancer causing agent, many water companies have switched, or are in the process of switching, to chloramine.


If your water contains only chlorine, then the sodium thiosulfate product is all you will need. If your water contains chloramine, there are other significant dangers for your fish. Chloramine is a chemical which contains chlorine and ammonia. If you use a sodium thiosulfate product, only the chlorine part of the chloramine is neutralized. Remember, ammonia is highly toxic to your fish. If the ammonia is not neutralized, you will be subjecting your fish to an extreme amount of stress and possibly their final day of existence in your aquarium. What is that you say? You thought that ammonia is removed by your biological filter? You are correct, however, the ammonia neutralizing bacteria in your aquarium is by nature automatically proportioned to the amount of ammonia being produced in your aquarium each day.

A sudden increase in the ammonia level without having the bacteria available to neutralize it, will many times lead to disaster. Yes, the bacteria will eventually catch up to the ammonia level, but I would not suggest you wait. The chemists of the world have again come through in the clutch and created a product which will neutralize both parts of chloramine completely. This product is also available on the shelves of most fish stores under several different names and it too is relatively inexpensive. Just as there is with chlorine, here is an alternative way to eliminate chloramine without having to use these products.

{The products manufactured for use with Koi ponds are ChlorAm-X and Ultimate.  K.O.I. does not recommend using other products.}

First, chloramine does not evaporate so you cannot simply let it sit in a bucket with aeration for 24 hours and then use it. The alternative method would be to put the water into buckets and aerate it as a first step.

Secondly, and this is a 'must do' item to perform, you will need to treat the water with the product of your choice as discussed above in the chlorine part of this article to eliminate the chlorine. Failure to eliminate the chlorine from chloramine will result in the bacteria in your biological filter being killed. I just gave you a big hint as to what the third step is. Yes, you are correct!! An established biological filter must be added to each bucket of water. When all traces of the ammonia have vanished, the water may be added to your aquarium. Although this method is not very cost effective, it will work.

Which do I have?

Rather than testing your water, the best solution is to go right to the source. Call your local water company. Simply explain that you have an aquarium {pond!} and need to find out what chemicals, etc., are in the water they provide to you. By law they are required to produce water quality reports for the EPA, which are to be made available to the public upon request. Ask them to send you a copy. You will be shocked to see what really is in your water. We hit upon the two big ingredients but there are many, many more. You will see columns of various ingredients along with their percentages. Most will not matter to you, however, a couple you want to look for are items which you can test for with the use of common test kits. They include phosphate, iron, nitrate, etc.

In conclusion

Quite simply, be sure you know what is in your tap water and treat it appropriately before adding it to your aquarium and ending up with a major catastrophe!

This article was written by Ed Keene from the Diamond State Aquarium Society, February 2014 issue of Gravel Gossip


!If you're not havin' FUN, you're not doin' it right