24 Chloramine
Description
This article is from the Beginning Fishkeeping FAQ, by Thomas Narten with numerous contributions by others.
24 Chloramine
One problem with using chlorine to treat water is that it breaks down
relatively quickly. Another concern with the use of chlorine is that
it can combine with certain organics (that may or may not be present
in your water) forming trihalomethanes, a family of carcinogens.
Consequently, many water companies have switched from using chlorine
to using chloramine. Chloramine, a compound containing both chlorine
and ammonia, is much more stable than chlorine.
Chloramine poses two significant headaches for aquarists. First,
chlorine-neutralizing chemicals such as sodium thiosulfate only
neutralize the chlorine portion of the chloramine, neglecting an even
bigger problem: deadly ammonia. The consequences can be devastating to
fish. Although a tank's biological filter will (eventually) convert
the ammonia to nitrate, the time it takes to do so may be longer than
what your fish can tolerate.
The second problem relates to water changes. One of the primary
reasons for doing regular water changes is to remove nitrates that
build up. If your replacement tap water contains ammonia, you'll be
putting nitrogen right back into your tank and it will be impossible
to reduce the nitrates below the concentration in your tap water.
Fortunately, tap water concentrations are relatively low (1 or 2 ppm);
you are more likely to have a much higher concentration of nitrate in
your tank.
Chloramine can be safely neutralized through such products as Amquel,
which neutralize both the ammonia and chlorine portions of the
chloramine molecules. The neutralized ammonia will still be converted
to nitrates via a biological filter.
Another method for neutralizing chloramine is to age the water while
simultaneously performing biological filtration. For example, get an
appropriately-sized (plastic) garbage can, fill it with tap water,
dechlorinate it with sodium thiosulfate, and then connect an
established biological filter to it. Just as in your tank, the bio
filter will convert the ammonia to nitrate, after which it can safely
be added to your tank. Note: you must add sodium thiosulfate to
neutralize the chlorine; otherwise, the chloramine will kill the
bacteria in your biological filter.
Alternatively, the ammonia can removed by filtering the water through
zeolite or carbon before adding it to your tank. [Note: folks report
mixed success with this. If you have concrete (positive or negative)
experience to report, please notify the FAQ maintainers.]
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