That's consistent with what Eeyore said: that it deals with the chlorine part, but not the ammonia issue that remains.
I discuss chloramine here:
Chloramine and the Reef Aquarium - Reefkeeping.com
Removing Chloramine From Water: Chemical Reducing Agents
There are two primary ways to remove chloramine from tap water. The first is through the use of inorganic reducing agents such as thiosulfate. Thiosulfate (S2O3- -, which actually looks like -OSO2S-) is an inorganic chemical that is typically dissolved in water, usually as the sodium salt. When added to water containing chloramine, a reaction takes place, destroying the chloramine. The electrochemistry of sulfur compounds can be complicated, and different researchers report different products of this reaction (extrapolated from reactions with chlorine itself, not chloramine). The products have been suggested to include sulfate (SO4- - and HSO4-),10,14 elemental sulfur (S),10 and tetrathionate (S4O6- -),11-13 and may depend to some extent on the conditions, including the pH and the relative amounts of compounds present. John F. Kuhns (inventor of Amquel below) has indicated that he believes that the reaction resulting in sulfate is the most frequently observed. The reaction for this process is shown below:
S2O3-- + 4NH2Cl + 5H2O --> 2SO4-- + 2H+ + 4HCl + 4NH3
Thiosulfate is also equally suited to dechlorinating free chlorine in water, and it has gained wide use in marine and freshwater aquaria. Unfortunately, the ammonia that is produced as a result of the reaction is still toxic. Consequently, thiosulfate alone is not always adequate for eliminating toxicity from chloramine.
Other products, such as hydroxymethanesulfonate (HOCH2SO3-; a known ammonia binder15 patented for aquarium uses by John F. Kuhns16 (sold as Amquel by Kordon and ClorAm-X by Reed Mariculture, among others) can be used to treat chloraminated water because they both break down chloramine and bind up the ammonia.
The reaction of ammonia with hydroxymethanesulfonate is mechanistically complicated, possibly involving decomposition to formaldehyde and reformation to the product (aminomethanesulfonate; shown below).15 The simplified overall reaction is believed to be:
NH3 + HOCH2SO3- --> H2NCH2SO3- + H2O
Even more complicated is the reaction of hydroxymethanesulfonate with chloramine, or chlorine (as Cl2 or HOCl). In this case, the products that are formed have not been established.
So are these useful products? That is, do they eliminate all toxicity from chloramine and provide none of their own, either by themselves or through their degradation products? I cannot answer that question. Almost certainly, using them is better than not using them if there is chloramine in the water. Is the toxicity eliminated for even the most sensitive larval invertebrates? Again, I don't know. Without knowing what the degradation products are, or without detailed testing on a variety of very sensitive invertebrates, I don't know how one would conclude that they are satisfactory (or not). Maybe such tests exist, and if so, I'd be pleased to hear of them. In the end, my recommendation is to remove chlorine and chloramine in other ways, such as through an RO/DI system as described below.
