My KitchenAid fridge water filter claims to remove ammonia/chloramines, plus a host of other stuff. However, this filter is like $40 a shot & lasts only so long .... so really only good for drinking water .... doing large water changes with something like that will cost $$$
BTW - I am reading your many threads about your bad water ... my bottom line opinion is to just use prime for your water and don't worry about ammonia of .25 ... your biologic filter should take care of that.
One other thought ... your water has up to 12 ppm of chloramines, which will give you 12 of bound ammonia (assuiming you add enough Prime). I am not sure if that high a level of bound ammonia will interfer with even the Salicylate test. Most people talking about Salicylate tests & bound ammonia are talking of 1-2, not 12! If the above quote is true, <that the salicylate test will eventually break down bound ammonia and read it as positive> then the higher the bound ammonia level to start, the less time you have to read the ammonia before it turns false positive.