"Chlorine is an oxidizer, which burns a fishes' gills. Chloramines, on the other hand, pass across the gills of a fish and into its blood, where the molecule attaches to the hemoglobin, acting like nitrite to induce methemoglobinemia. The toxicity of chloramines is affected by pH, I'm reading at
www.fishdoc.co.uk, with Chloramine-T more toxic at lower pH. Fish stricken by chloramine poisoning are sluggish and respire heavily. But chloramines have been inflated into a bugaboo by some packagers/distributors of various water "conditioners." Aquarium Pharmaceuticals, for instance, characterizes chloramine as "deadly" in corporate literature. Nevertheless, the not-invariably-"deadly" Chloramine-T is currently being studied by the U.S. government as potentially important to fish hatcheries in controlling bacterial gill disease. Studies at UC Davis have inspired widespread use of Chloramine-T to kill pathogenic bacteria and parasites in koi ponds. A professional assessment I trust is this from John P. Grazek: "The addition of sodium thiosulfate will neutralize both chlorine and chloramine. However, ammonia is released when the sodium thiosulfate combines with the chloramines, and this could be a problem to fish where there is little or no biological filtration." (in Aquariology: Fish Diseases and Water Chemistry, Tetra Press 1992). In chloramine, two chloride ions are bound to each ammonia molecule, and that's why you're usually advised to double the quantity of sodium thiosulfate you'd use for chlorine alone. In acidic water, the ammonia released would largely be ionized to its non-toxic form, ammonium. In a planted aquarium NH3/NH4 would be rapidly scavenged by the plants.
Testing for chloramines. If you're testing for chloramines, make sure the test kit you've borrowed is testing for "total chlorine" or "combined chlorine," not for "free chlorine." A test for "free chlorine" would misleadingly read zero in chloraminated water.
On the other hand, when your tapwater tests positive for ammonia, this is a sign that your water is being treated with chloramines.
The Washington DC water utility offers a document "How the conversion to Chloramines affects your fish" generated by the U.S. Army Corps of Engineers, which injects a note of sobriety into this sometimes panic-inducing situation. Being a public agency, the Washington Aqueduct couldn't recommend any commercial brand, but in general they recommended four general methods for neutralizing chloramines: 1. activated carbon in filtration, 2. sodium thiosulfate, 3. commerically-available de-chloramination products ("some simply remove the chlorine, while others 'lock up' or detoxify remaining ammonia"), or 4. a chemical agent plus a biological agent ("bio-filter") to remove the ammonia. (You should already have known all this, eh?)
If you're depending on 1. filtration with granular activated carbon to break the chloramine bond, make sure the carbon is fresh and the filtration is slow. Since some ammonia is likely to be freed, one way or the other, you have an additional incentive to de-chloraminate before you add water to the aquarium.
Re: methods of removing chlorine from tap water
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Originally Posted by Graham
..Aeration does nothing if you don't break the bond first. I tried it: after 7 days aerating in a bucket and the ammonia was still there until I added a dechlorinator and the ammonia dissipated...took sooo long though..Chlorine is in Sydney dam water to make it safe for consumption. It bonds to the ammonia and you get chloramine right? I can tell you 1. aeration does NOTHING to move it, I've tried and 2. If you added it to a biological filter without FIRST neutralizing the chloramine, it will kill your bio filter. Maybe you just don't have loads of crap in your water like some of us folk which is good for you
Because the ammonia is "locked up" by the chlorine, aeration won't get rid of the ammonia, (I've tried it to 10 days undechlored aeration with 0 movement in readings) until I neutralize or "unlock" the chloramine bond so the filter can process the little bit of ammonia left over.....straight out the tap mine is at .25ppm and the same after 10 days undechlored with aeration. I still can't add it to a tank without a dechlor...but going to try the sulphate next...
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