What about this:
Guest Editorial
According to Roddy Conrad:
Sodium thiosulfate instantly takes care of the chlorine in chloramine, as well as straight chlorine. The reaction to get rid of the chlorine with either chloramine or chlorine is instantaneous on mixing of the sodium thiosulfate and the chlorine or chloramine.
The reaction of sodium thiosulfate with chloramine produces ammonia. Assume you are doing a 20% water change and there is 1 PPM chloramine in the water. 1 PPM chloramine neutralized with sodium thiosulfate becomes 0.2 (20% water exchange) times 17/51.5 (molecular weight of ammonia divided by molecular weight chloramine) = 0.06 PPM ammonia level in the pond. 0.06 PPM is too low to even measure, and is safe for the fish anyway! My point is that it is perfectly safe to dechlorinate with sodium thiosulfate unless you are doing a 100 % water change and there is a huge 5 PPM chloramine concentration in the makeup water. Only then can the ammonia from the chloramine reaction with sodium thiosulfate get up to a 1.5 PPM ammonia level to give a possible real fish problem. Even then, please remember koi shipped in bags normally arrive at their destination in water that is 5 to 10 PPM ammonia level by measurement, and that is done all the time by the koi handlers without giving it a second thought. Yes, that level can do damage to the fish if you allow it to continue, no argument about that.
So all those warnings about using sodium thiosulfate to dechlorinate water containing chloramines is just so much hype from folks making a profit selling the ammonia binding products to my way of thinking about the actual technology in action.