I lifted this from Corrosionjerry on the Alberta Aquatica Forum:
A few years ago, I asked Greg Morin at Seachem what does Prime do exactly to Chloramine. Here are my questions (in bold) and his responses (in italics):
1.) what happens to the Chlorine?
it is reduced to chloride, rendered totally harmless
2.) what happens to the Ammonia? Does pH affect the toxifying of the Ammonia?
The ammonia is converted into a non-toxic form (not ammonium). It is
converted into the Schiff base of an aldehyde (R2C=NH) which is
One person has said, "true they will detoxify ammonia NH3 to ammonium NH4"
Not the case, see above, a simple conversion to ammonium can only
occur quantitatively below pH 7, above pH 7 you would have some
ammonia and some ammonium.
The bacteria do use this non-toxic bound ammonia, but they use only
what they need... they do not "see" an excess of "ammonia" for them.
The bound ammonia converts very slowly back to ammonia but at a rate
that is much slower than the rate at which the bacteria can remove
it, so the net effect is you see no free ammonia rise in the aquarium
and the bacteria continue on just as they normally would.
(I mentioned using a holding tank to 'age' the treated water)
This is a good suggestion, it is always best to neutralize the change
water before adding it to the aquarium, however one can add change
water straight away and then add a dose of Prime based on the total
volume of water and not the change volume. Not ideal but one can
generally "get away" with this if they are not inclined to premix the
change water before adding to the aquarium.
Also, any test for ammonia will show positive when treated with Prime
or a similiar product because all commerical ammonia kits on the
market converts ionized ammonia and bound ammonia to total free
ammonia by raising the pH to 13+ which destroys the Prime-Ammonia
complex, thus giving a false impression of the level of toxic free
ammonia. To measure only toxic free ammonia one can use either our
Ammona Alert or MultiTest:Free & Total Ammonia which uses a sensor
technology that avoids the issue described above.
Hope that helps (probably more info than you wanted to know) - Keep using Prime and you should be okay.